Don't think impossible. I had one of those bikes for many years. I can get you performance pieces from Malossi if you would like for it. Many pieces are interchangable but the bike are all in japan and europe.
50cc.eu Onderdelen, scooters, bromfietsen, Parts, scooters and mopeds is also a good place to get parts and they will gladly ship to the US. Also tanks seem to appear on Ebay alot so just keep your eyes open. I also have a contact for lots of parts if your interested. He has a barn full of them.