well all i know is that you get it from that Navy Base in San Fiero and thats the only place where you can get it unless there is that mission that one of you guys were talking about...and if your not against cheating there is the never wanted cheat put it in before you start and put it in again at the end when you are about to save..
Never Wanted Cheat= Circle, Right, Circle, Right, Left, Square, Up, Triangle
Hope I Helped
franDOGG