What about running adhesive flat wire? Essentially a piece of copper ribbon backed with adhesive? My wife's Breezer Uptown infinity has the wiring run inside(not just inside but INSIDE like molded into the fender) of the plastic fender and then just buttons basically connect to the rear light and from the wiring on the frame. It's a really cool setup with no need to run wires inside of the fender. For how much we paid for that thing it better of came with snazzy parts like that.