does it have the crazy "black box" type, with the 9V+ routed through it?
if so, you can indeed use a regular switchcraft stereo 12B, but you'll have to re-wire a little.
you'll connect the 9V+ (red?) wires straight together (so the 9v+ goes right to the preamp), then find and separate out the 9V- wire coming from the battery clip, and run it to the sleeve instead of to ground.
i do this on music mans all the time to lose that crappy plastic box jack; the trade-off is that sometimes if you plug in the bass while the amp is on, you'll get a momentary noise as the preamp powers up. (you shouldn't be plugging in while the amp is "live" anyway, so it's not really an issue).
Guitar Repair Gnome
Alpha Music, VA Beach