I have a Givi windshield I love it but even with being careful with it, it looks a tiny bit scratched/hazy. I bought a MacGuires plastic headlight polishing kit for $19 on sale at the auto store and have used it successfully on all my plastic windshields(Silverwing and BMW) It is a kit w paste and a buffer that fits into your hand drill and it polishes them and removes the haze/tiny scratches. Makes them shiny again. Also have successfully cleaned up helmet shields. It is worth a try. Maybe others have had success with other kits too. I can see through the windshield better now when the sun is low on the horizon.

Best damned stuff in the whole, wide world, bar none!