The movie packs had a hole drilled on the inner side of the banjo and did not run the wires through the bolt. It seems like that would be pretty difficult to do and that drilling a hole would be far easier. Here is how I recently did it:
Hope it helps.
Edit:
The pic posted above is of vintage banjos, below is a pic of a replica banjo that I was previously using. Drilling the hole is pretty easy.
