The line labeled "PCV" is the line that purges the stored vapors to the carb/intake by teeing into the PCV system. You can plug the line and plug the canister, but the canister won't be able to vent and eventually will get filled up with condensed gas vapors (liquid gasoline). One fix for the broken port would be to epoxy it back on. JB Weld would likely do the trick, just make sure to thoroughly clean any grease/oil/dirt off the area that you need to fix, and be sure not to epoxy over the opening of the port.
As far as replacement canisters go, the factory canister is no longer made for the 4.2L. Just look up an Emissions vapor canister for a 1991-1995 4.0L YJ. (STANDARD MOTOR PRODUCTS Part# CP3045; Mopar Part# 53030500). I got mine from Rockauto.com. You may have to squeeze it into the canister bracket, but you shouldn't need to mod anything else other than drill open the plugged port to use for the carb bowl vent.