Thanks to Smaz for providing this guide and the descriptions and images that follow.
Golden Wumpa #1 - Wumpa Island
Not long after jacking your first Ratcicle, you will be lead into a cave in which has several wall mouths which gush out water. Sneeze-freeze the first one you come across, to the left of the entrance, by blocking and pressing the attack button at the same time. Jump on it, as a ledge, to reach the Golden Wumpa Fruit on the other side.
Golden Wumpa #2 - Frozen Coast
After meeting your first Magmadon and battling in a small arena, you will come across an iceburg, which will take you to the next area. The first area has a Golden Wumpa Fruit on a shallow water path as soon as you enter the area. You will need a Ratcicle to surf on the water and retrieve it.
Golden Wumpa #3 - Ice Prison
In the first room, after jacking the first TK you meet, travel away from the screen until you reach its back. You will find a small gate with a Golden Wumpa behind it. Move the blocks out of the wall, in order to use them as steps to reach the raised floor, to the right. Follow the path around and towards the screen in order to find a button in which you'll need to spin on, in order to open the gate. Head back and collect the Wumpa Fruit.
Golden Wumpa #4 - Ratcicle Kingdom
After coming back to the Ratcicle Kingdom, with a TK, you can flip the switch on the wall, behind the statue, in order to turn the large ice Ratcicle statue to point to the left. Climb on top of it, before it reverts, and jump off of the arm to the left, holding the button to fly to the Golden Wumpa, in the air.
Golden Wumpa #5 - Wumpa Island Pathway
On the way back from the Frozen Coast and to Wumpa Island, after climbing the water mountain section, you'll come across two cubed blocks, before you have to head down. Climb on top of these blocks. You can either use the TK to move the blocks, on the floor above, out of the way, or simply double-jump up to reach the platform, and then jump on top of the blocks on the raised floor. Behind the blocks sits a Golden Wumpa.
Golden Wumpa #6 - Wasteland
At the gate, just past the Rhinoroller rails (it needs to be opened via a Rhinoroller switch), is a pathway just to the right. Follow this trail to find a curved wall, which you'll need to roll up, to reach the floor, above. Upon reaching that floor, roll to the left and you'll be launched upwards and around the ceiling, collecting a Golden Wumpa in the process.
Golden Wumpa #7 - Wumpa Island
Bring a Rhinoroller from the Wasteland and start heading towards the waterfall which takes you back to Crash's house. Not long before this area is a pathway which heads towards the screen, just after the side-on camera section. Head towards the screen to find a gyser. You do not need a Ratcicle to freeze the gyser and reach the platform, above. Simply chimney-jump up the wall, to the left, and reach the top, where the x2 Mojo multiplier sits. Then, store your titan/mutant and double-jump to the platform on the right. Once there (you may need to hold the attack button for additional air-time, before landing), use the Rhinoroller to slide along the rails to the circular section in the wall, ahead. Once in the wall, boost up the sides in order to reach the top. Once there, store the Rhinoroller and then chimney-jump up the walls, once again, to reach the Golden Wumpa that sits up top. Phew!
Golden Wumpa #8 - Evil Public School Path
You will need a TK and Rhinoroller for this. Use the Rhinoroller to gain access to the pathway and then boost up the curved ledges near the start. Head left (rather than right) to find an Ice voodoo doll and a lever/switch. Using the TK, pull the switch down to make a platform appear. Jump on it and it will take you upwards. From there, hold the jump button to fly across the platforms to the left. Keep heading left until you eventually reach more Golden goodness.
Golden Wumpa #9 - Evil Public School Path
Using a Rhinoroller, after the large icicle wall, boost across the floor and then jump onto the small ledge to the right, just before the dip in the floor. Once on that platform, boost and jump again to reach the Golden Wumpa in the air. It's just before reaching the end of the area and the school grounds, itself.
Golden Wumpa #10 - Wasteland
On the way to the Junkyard, and in the area beyond the large metal door, you will find yourself boosting around the walls using a Rhinoroller. Stay to the top layers and you'll find the Golden Wumpa on the roof of the first curved wall section.
Golden Wumpa #11 - Junkyard
Near the 3rd Junkyard voodoo doll, across the first piping and above the platforms of the sludge-floored section, sits a television set on its own, to the left. Simply smash it up to retrieve a Golden Wumpa. This area is just after the friendly Sludges.
Golden Wumpa #12 - Mount Grimly Path
You will need a Spike to gain this Wumpa Fruit. Just across the windy area, on the way to Mount Grimly. before the pathway stretches forward and not to the side, sits a spikey blockade in which you will have to use the Spike's special attack in order to get through. Once through the spikes, follow the pathway down to be greeted by several Znus and a Golden Wumpa Fruit.
Golden Wumpa #13 - Mount Grimly
You will need a Ratcicle to gain this Wumpa Fruit. Not long after entering the mountain, itself, is a climbable wall which leads down to a water area. You will either have to go to Wumpa Island or the Frozen Coast to obtain a Ratcicle (Wumpa Island is the better option) and then teleport back to Mount Grimly with one, after completing Uka's mission. Once having obtained one through long and tough means, head down to the shallow water and surf around to get to the Golden Wumpa. Make sure you don't touch the deep water, like I did, otherwise your Ratcicle will disappear, forcing you to do it all over again and curse your own existence. Maybe that's just me?
Golden Wumpa #14 - Mount Grimly
The final Golden Wumpa needs a TK to obtain. You will reach a room in which several debry will fall from the ceiling, causing you to slow down time in order to use them as platforms to cross. Once passed, head to the right (and not left) to find an area riddled with moveable wall platforms. Using the TK, carefully pull them out and jump on to them. This may take some time, given how many platforms there are. Once at the VERY top, you will find a small hole in the wall (it's almost invisible). Jump into it for it to take you to a new area. Follow the path to the right to find a Golden Wumpa Fruit. Yum, yum!