1963 Vespa 90 piston rings

Hello all. This is my first scooter I'm working on and I'm hoping that somebody can help point me in the right direction with a problem I'm having with piston ring availablility... or lack of. This one is a 1965 Vespa 90 model and I can't find the piston rings anywhere. Does anybody know who has these? I have spoken to a couple of different scooter shops but to no avail. I'm finding that there is two different size piston rings on the V9A engine. It seems that the change occured in 67 and the piston ring is a bit wider and will not allow the cylinder to slide over the piston on the earlier models. Any help would be greatly appreciated.

 

Thanks again.

Steve