Boss VF-1 Effect Processor

I picked up a VF-1 a while ago for pretty cheap (probably in part
because it has a busted knob).

It's the Power/L-R Input Level Knob that's the problem. It all still
works, but I have to use needle-nose pliers to turn the knobs. It's
not an urgent problem, as I don't need to change the levels
frequently, but I would like to fix it at some point, if I can.

So, anyone know the proper name of this part ("dual pot switch" brings
up some Google hits, but I don't know the pot values, nor where I can
find them out. If there a VF-1 schematic out there somewhere?) Or do
you reckon it's something custom-made for this unit, and if so anyone
know someplace to get old Boss replacement parts?

Thanks,
Joshua