I've quit buying special firing pins for these guns. I just use an AR firing pin, chuck it in the lathe, and cut .030 off the face that contacts the bolt. Use a tool with a small radius on the tip for this.
My go to gun shop is Hammer Down Guns and Gear in Ontario, Calif (Vineyard and Riverside Av) I've found these guys to be very helpful and knowledgeable. Phi is the master of everything AR. He makes AR's in 7.62 x 39 run like a swiss watch. And their prices are fair! Try them out if you're around here.