My wife has a really cool watch (not an expensive one) that has a plastic lens. She is an esthetician and does nails and after a month or so her lens get hazy and she brings it to her jeweler and he polishes it with some sort of liquid and it comes out just like new and it takes a few minutes.
I suggest you go to a local jeweler and find out if you can buy the stuff off him or try the stuff that Meguiar’s sell for this. If I was you, I would go out and buy a old used light like something off an old Ford Taurus that is almost completely hazed out for a few bucks and try it to see if both alternatives work. If so, then your not buying an expensive replacement headlight for several hundred to a $1000+ for a new one.