There was a run of the pre-B mags some years back but I have not seen any in quite some time and it's not likely as things are now that anyone is going to produce any. Personally I would buy a couple regular 75B mags and carefully make whatever mods need done to allow them to function properly. The "B" mags are readily available and often at really great prices.
Greg Cote is a fine source and while some things may be out of stock he regularly gets them back in.
Last time he had "B" mags on sale I snagged a pile of them for my full size and compact CZ's.
Thanks, good advice, and probably also a reason to pick up a CZ75B finally. (I do have a few B mags for my full-size Canik, but a few more can't hurt.)
I will probably keep my eyes peeled at gun shows, but more for fun than for a practical source.
I was thinking about Cajunizing the pre-Bs, but I'll probably finally retire them to the safe.
Maybe I shouldn't have bought so many P-mags the past few years, and focused on other guns/mags a bit more.