Piston rings.

I need new rings for my 75cc Vega rebuild. The piston is a Vertex aftermarket one. The bore is 46.8 but here's the problem; the Vertex uses 2.5 mm thick rings not like the standard 2mm. I've actually found some new 2mm rings but to reuse the piston I have ,I need 2.5. Does anyone know who might supply them? Believe me I've Googled like mad! Vespa 90 rings are often used for Vegas but they are 2mm too.
Paul
Paul