I have seen a few for sale lately. Legacy has one and there is another on GB at the moment. Plus the two coming up at RIA this week end.
https://www.rockislandauction.com/de...t-rifle#detail
https://www.rockislandauction.com/de...g-mp-44#detail
I could not tell you haw many are in the BATFE system. Cant be that many.