Checkmate continued to make them through the ban, and we got a bunch at work. They are more or less indistguishable from 1960s and 1970s production USGI magaines except for the LEO stamp and the fact that the welds look more prominent, and somehow sturdier. There was at least one other manufacturer who made them during the ban, and I contacted them about making some (don't remember their name right now). It would not have been economical for us, though; I think their minimum order was in the 100s, and we didn't have THAT many M14s, but price got down around $15-25 per mag in bulk. We stalled just long enough for a big batch of a couple thousand NIW M14 magazines to come up in DRMO, and we ordered enugh to supply our M14s for decades.
With increased M14 usage for both the military and for local LE (DRMO sells them dirt cheap, less than the cost of a new magazine, actually), and the M1A market, I don't see why they would not make more, or at least someone will.