Like Joe said, only other option would be to get a genuine belt and that would be an expensive exercise.
As for the age of it, you have a guess how old mine is and i will have a guess how old yours is. They probably made them for well over 20 years. So without a picture at minimum theres no point even guessing. Someone may have info on model numbers by year but i doubt anyone here has it.
The numbers on the engine cowling will tell what year the motor was made. Assuming that is the original engine it will tell you what year it was made.
