Depending on what you expect from the bike maybe fresh rings will be enough.I expect my bikes to work for a living so I would be measuring the bore to see what wear there actually is. I recently did a top end overhaul on my G3l using a new old stock piston and rings I'd had in stock for years. I'm very lucky in that I have a brilliant engine shop who work to very high standards.Every engine I build now has the piston skirt coated and baked with a low friction,high temp coating.It makes the engines run cooler,use less oil and last longer - And allows closer piston to bore clearances.
But I am fussy... If you are happy to do a hone and fresh rings then Cox and Turner Engineering will supply just about any piston rings you can think of.