I blew out the back window on the shell of my Toyota work truck years ago. I had a wheelbarrow on the roof, only tied off to the rear bar on my rack over shell. As I hit 50mph the wheelbarrow lifted and rotated over the rear bar of the rack, driving both handles through the back window of the shell. Boom!
I replaced it with plexiglas.
Now that I think about it, that's pretty much what's happened with my Hawk. I blew out the door window, losing control of the door during a wind storm in Death Valley last winter. And now it's been replaced with plexi.
Only downside is that it scratches easily.
To finish the story about the cap on my dad's truck, the replacement I bought only lasted a few months until my dad did the same thing.
I replaced it with polycarbonate (a.k.a. Lexan). It's considerably tougher than acrylic (a.k.a. plexi) but considerably more expensive too. It is often used in things like boat hatch covers, eyeglass lenses and a host of other products where strength is needed. It isn't as sensitive to UV so doesn't start to fog as quickly. While certainly more scratch resistant than plexi, it isn't anywhere near as hard as glass. That's why eyeglass manufactures coat polycarbonate lenses.
You should be able to get polycarbonate a most industrial plastics outlets. I works very similar to acrylic
