yep, Both Plus-X 5231 and 7231 and the old and new version of Plus-x reversal are all discontinued. (doubt if they ever made more than a couple of batches of the "new" Plus-x Reversal.
5222/7222 is the only B&W movie Negative. I have never heard of a Tri-X negative movie film. (there are two version of Tri-X reveral but both in 16mm only)
There was a 4X negative (ISO 500) at one time. as well as XT pan. (ISO 25) I only ever got 100 ft of each, The 4X was rather grainy but the XT was a VERY nice film - it was intended for shooting background plates for rear projection and of course those were no longer done in B&W)