Since nobody else will give you a straight answer...
No, you cannot get a fisheye for a gopro, 2 reasons why:
1. It has no threads that you can screw a lense to.
2. It has practically a 180 degree lense, and a fisheye is used, not to get a cool effect, but so you can get closer to what you are filming
My guess is that you don't own a gopro and know that it already creates a semi distorted effect, and that you can get extremely close to the subject your filming. A fisheye will not increase how good your skate edits are, and infact can look much better without them