unless they have been particularly annoying, id have to agree with jinks, and say that ANY expansion chamber should fit it, as they should all be standard thread sizes.
The same as all vertical regulators.
also, PBreview is probably quite a good bet for info. Maybe also try the PBnation.com forum, they usually have a wealth of knowledge.
As for barrels, any barrel that is the right bore size for the paint you most commonly use is advisable.
What paint do you shoot / does your local site use?