Rick, I assume that you are talking about a Mod. 500 pump with the tang safety. Mossberg one upon a time said this was a factory only thing. As I recall, "and those of you who know me I ain't doin that so well" Mossberg will sent you new safety parts if you swear to them you know how to put it together and fit it than they do. If you really don't know let your smith have it. Sounds like the whole thing needs looking at. Heck, they even put em on with those anti tamper public restroom screws!
Be Safe, Hank