nole76, sometime a while ago, if memory serves, there was some discussion on the forum about original AS green rub rail availability and I believe somebody, maybe Captain or Wilson found the original manufacturer who is still in business. I think the name of the manufacturer was mentioned. It may be the end caps were a standard item and not unique to AS and that they're still made.
Sorry to be so vague on the details but hopefully this will point you in the right direction. If you do find the caps, I need a pair too. Mine are oxidized & have turned green/blue/black & are glued on.