I purchased a large sheet of Makrolon AR which is similar to Lexan. this product has UV coating that decreases yellowing that is typical for polycarbonate plastics. This is the product that was used (and may still be) by NASCAR when I bought it ~10 years ago after I cracked my second windshield on the track. I cut the windshield out on my bandsaw and it has worked perfectly. Go to this link for pricing info:
http://k-mac-plastics.com/hyzod-poly...ate-sheet.htmg
Your local plastics distributor likely has it or can get it for you. I did have to buy a large piece (4X8 ft) so I have enough for 2 more windshields if I ever need one. This should be much cheaper than $350 each if you have the time and a band saw and someone to share the piece with.