Does anyone have or know where I could get a shell stop for a SAVAGE 12 GUAGE 1921 PUMP SHOTGUN , I believe the MODEL 21 is the same gun. A friend has a heirloom and wants to get it out hunting again. This shell stop is a little different from the usual kind in that it only fits down one side of the receiver and has a "U" shaped piece on the end that controls the feeding of the shells from the mag. THANKS.