As others have stated, an original one would be the best, however; they are hard to find. There are reproductions available online, but most are made from plastic--the originals were made from hard rubber. Galazan offers hard rubber Trojan reproduction butt plates and they're on sale! They offer two sizes, here's a link to the larger size intended for 12-ga. Trojans.
http://www.csmcspecials.com/Parker_T...te_p/pb310.htm