I would take a thin guitar string... high E, presumably; bend it in half and form the bent end into an eyelet a little smaller than the inside of the fork crown (you have to imagine this shape to the best of your abilities). Then squeeze that into the hole. It should open up inside the tube. Then push your electric wire up from the dropout end. When it's gone as far as you can make it go, it should be through the guitar string; so now twist and pull the guitar string out. It will close up around the wire and, hopefully pull it through the hole.

Well, it's just an idea.

Good luck!