Try some plastic window polish. You can get several grits/grades made just for polishing the plastic windows on convertible tops. I'm pretty sure Moss sells them. You would want to start off with the lower/courser grit polish, then follow up with the finer polish. I see that Moss sells a brand "Renovo", Plastic Window Polish. I haven't tried it and don't know if it comes in different grits. I'm pretty sure I've seen it at the local auto parts retailer, or you might go to a convertible top repair shop, and see what they recommend. I had two bottles of it at one time, but can't find them know. One bottle was for deeper scratches, the other for getting rid of the foggy/hazy look of the plastic.