I'd suggest you look at this link for piston manufacturers:
http://www.performancemarket.com/Contact the manufacturers directly, and ask them to send you their catalogs. If you explain what you are doing, to the right person (usually not too hard to find) you'll likely get plenty of help. If you'll take the proper measurements, you can cross reference them with the numerical listings in the catalogs.
If you have problems, or need assistance with the technical end of it, send me an email and I'll try to help you.