I am attempting to solve the same problem - vapor leaks galore on my 95 S4, replacing the canister and everything else in the evap system. I have not interest in deleting the evap setup (hasn't served me well to do this on any other car with such a system..)
It seems the factory canister and it's catalog-replacement part are all but extinct, I can find only used parts on eBay which I dont want to do.
JAE and many others, including the GM F Body community, seem to be suggesting a canister from a later model GM truck that is about the same physical size along with what is described as the same solenoid, but standalone, to be plumbed in.
Has anyone else taken this same approach? Are the parts I'm looking at the best choices? Any other alternatives or someone with their hands on some NOS canisters?