No problem. Ebays actually not that bad. Just make sure to hook the paypal account up to your credit card and not a bank account, and if anything goes wrong, you can charge back through the credit card. Credit card companies make charge backs for unreceived or damaged merchandise really easy. If you hook it up to a bank account, good luck getting any money back, and paypal can actual pull money from your account or put a hold on funds if a seller (or buyer, if youre selling something) disputes the transaction.
Oh and always make sure to check the shipping charges. Some sellers make major money inflating the shipping (ive seen 300+ dollar shipping on a
gas cap)
If you really want to buy from someone local, check your local performance bike shops (not the places that specialize in gear). If you have the specs, im sure there are piston companies out there (wiseco, vertex, hundreds of chinese vendors) that either already make a piston that will fit with the profile you want, or will make one to your spec. The shop will have the book or know who to call. But youre probably looking at big dollars. Or you
may have luck with honda, but checking bikebandit it seems like 450 pistons are no longer in stock so i dont think honda will be able to get them.
Or someone on here might have a set to sell you. Good luck