/cgl/ - Cosplay & EGL

I asked this previously in another thread but I have come across a few problems.

I'm making a motorized patriot cosplay from Bioshock Infinite.

Anyway, I plan on having the back wheels actually move, or at least have the ability to move for a little bit for the sole purpose of videos/etc. I've looked into DC and servo motors and directly mounting them to the wheel but the problem is the wheel forks don't have enough room for me to just shove one in there. I know I'm asking for a lot when I say this but, does anyone have ANY robotics experience and could toss some ideas my way? It doesn't have to be elaborate or even look exact, I just want the damn wheels to move haha. Pic is what i'm working with, all unpainted and they're mounted on the forks with bolts as placeholders until I figure out how the fuck to do this.

thanks in advance.