The Novus products work well if you're willing to put in the elbow grease. I use it on my Jeep soft top windows. It is a three stage product that polishes and fills scratches. I've also heard of other Jeepers using Lemon Pledge with excellent results (I don't know why Lemon ?)
Personally, I'm getting rid of my plexiglass in my machine. I thought about going to lexan, which the glass co said was much better for scratch resistance, but decided on glass.
I'll be able to SEE again out the side windows!!
Vance