I had a local glass shop cut me a piece of 1/4" plexiglas for under $50. I drilled holes in the corners and installed rubber grommetts and attached it with zip ties to the frame around the window. I've had it for almost 2 years and I don't think it has any noticeable scratches. It has water spots and some dirt on it from ocassionally leaving it out in the rain. I do drive it thru the woods some and some new growth tree limbs do hit it but still no big scratches. The glass company had another type of glass (not glass glass) that was 50% more money but I wanted to try the plexiglass first to see if the scratch horror stories were true before I paid more money, for me they haven't been true.
If I had it to do over I'd still buy the plexiglas or maybe pay the extra 50%, not positive about that. I'd also make the windshield 2 pieces. A upper part (maybe half) hinged to a lower part and be able to lower the upper part in the summer and raise it back up in the winter like golf carts or like a golf cart I used to own..