Hello!
I've fabricated aircraft canopies before, and so I believe a windshield can be done, too. I would advise against those collar stiffeners and stuff like that - the thing is they turn yellow or orange after a few years and this is annoying. You are a lot better off looking for good quality sheet plastic like Vivak or stuff like that.
Then the trick would be to make a positive form for the windshield you need - like a plaster of paris casting of the original or something like that (it needs to be really smooth!) and then heating a piece of that clear plastic and pulling it over your form - this might give you the shape you need. After that it's a matter of careful trimming and fitting it to the remainder of your model.
Hope it helps - good luck with your builds and have a nice day
Paweł