I would think like a magazine warehouse type place, or gunbroker and eBay. The little extension helps to draw the pistol and control it while shooting.
I kind of liked it, a nice solid feel, not like the little tang of metal that followed in the DA version.
These were modified to hold 6 rounds, they came from AMT to hold 5. They literally needed about 1/16th
of an inch more to get the 6th round in.