"BigBritches it does not look like the pistol you have is set-up for a stock. The pocket rifles had a milled out slot on the bottom of the grip frame and a threaded hole in the back of the grip frame(which I can see yours don't have). "
This is one of those times when I should have looked before I opened my mouth. Well at least everyone now knows how they attach. I will add that most had a longer barrel than yours(making yours rather uncommon).
Just walking on the edge of of my grave.