I was at Pep-Boys (auto parts place..don't know if there are any in NY) a few years ago and found some metal polish that goes by the name of "Blue Magic Metal Polish Creme" that worked really well for cleaning plastic lenses on cars.
My friend tried it on his old Acura Integra that had some really foggy/yellowed headlight lenses. It took two or three applications of the stuff, but when we were done the lenses looked almost brand new.
Over the years I have used this stuff on a lot of plastic/polycarbonate/plexiglass surfaces and it works really well for restoring the surface.
I was a little skeptical about using metal polish on plastic, but IIRC, it says on the little canister that it's safe for plastic. If you don't have a Pep-Boys, I'm sure just about any chain store like Autozone or Checker/Schuks/Kragen/Advance Auto/Discount Auto (all 5 have the same parent company) should carry it.