Anybody have any imput or experience on finding/installing an on-board pre-amp on a G&L JB 2?

I like the bass but spoiled by the active electronics on some of my other basses (Music Man Sterling, '72 Fender Jazz Bass w/ active EMGs, '90 Fender Jazz Bass Special 5-string).

So far Bartolini has a set-up closest to my desires. I DON'T want to modify the body in any way, if possible.

Thanks for any help in advance.