I haven't seen them for sale at Oveready for a couple of years.
They occasionaly come up on the WTS here, but you'll have to join the queue.
Sorry to be the bringer of bad tidings. If you find one, you won't be disappointed.
I am also hoping heavily for a comeback of the triad tail caps, I owned 2 in the past, one for my M2 and one for my 9P, both of which I have sold... I hate myself everyday for selling them, if I knew they were going to be so hard to buy again I would have treasured them like my children lol. Hopefully, with enough recognition in the market for a comeback, a small batch may be made to help us that need them so bad.