I made my own out of polycarbonate. I am sure I will have to replace it, and it will scratch but it coslt me $40. So I can make a couple. I wish I would have made it a bit shorter. I think about 16'' height is good. I just left the bottom straight across and put some fuel line under the middle to keep it from wearing thru or scratching the dash. Works really well and doesn't get dusty with the top and bottom letting air thru. I will attach pics when I get a chance! I bent it at the top to give some strength.
I used plexiglas for a windshield on a tractor. I built the frame, then bolted the plexiglas to the frame. This is fine as long as the temperature is reasonably close to the temperature at which you mount the window. As soon as it gets much warmer, or colder, the plexiglas does some serious volume changing, which causes it to stress against the bolts. After that, it cracks.
I am designing my next Prowler windshield around 1/4" plexiglas. I am looking at over-sizing the holes, and using as few bolts as possible, to counteract the stress cracking. Will report after it is built and run a while.