Col, is it the Rossi Puma you are talking about?
[Edit] I havn't seen anything on Numrich, or Brownells for a firing pin for that Rossi 92. I tried also looking for a Winchester 92 firing pin. Nothing at all, i'd sugjest checking out this site
http://marauder.homestead.com/files/Rossitune.htm. And contact them to see if they could know where to buy one.