I'm surprised 4G010H3R0 did not jump on this sale already!
to help sale:
ball detents seems pretty beaten up (I guess they're almost in the "gooey" stade) and will need to be changed.
Cosmetic states looks kinda good (for used vintage guns), especially those cylinders!
If you're willing to part one or 2, I might be interested.
If you're OK to ship international, I'll relay your offer to a big french forum (these 3357 are pretty rare in Europe).
About .50 paint, it's quite easy to find: in the worst case, just buy some "flying colours" paint (for kid's, spring-powered, paintball guns).
Tomahawk, Dark Sports, Celtic Paintball, Diablo and Spyder/Kingman are all producing .50 paintballs.
I think Nelson produce it too, but they are not really into EU market so I'm not sure of that.
Hope that'll help!