although the "proper" piston rings are always best for the job if you are stuck and cannot get the size you want for your favourite old bike you can try these people:
http://www.dlastore.com/e_store/cylinders-pistons-mufflers/individual-piston-rings.html?cat=30&diameter_range=14the prices are amazing and the delivery is surprisingly cheap, I have purchased rings from them before, they come from Greece, and although they were cast iron rings compared to the steel original rings they gave good service and were certainly excellent value for money.
Note – most of the sizes come without notches for 2 strokes so you have to file/cut them yourself
