[KensRedZed]

A friend of mine makes canopies for his model aircraft. He takes a small piece of pine and sands it to the curve of the window. Then cuts up a Pepsi or Coke bottle because he umm... doesn't like to spend money. Then gently melts the plastic over the curved wood with a hot air gun on low. The wood mold is a bit bigger than the actual window so he can trim a clean edge exactly to the window.

It should not take much time to make a window mold. You can make a few windshields and use the best one.