Before you buy the vinyl window, find the shop that will do the sewing. They need a long arm sewing machine and you need to r&r the canvas for them probably - a major issue.
The advantage of doing it by hand with an awl is that you can do it with the frame attached. Akward but do-able.
Don't assume thicker vinyl is better. It is a pain to puncture with the awl. It is not necessarily any more U.V. resistant and may be more brittle/stiff in cold temps.
this gives you an intro to some of the brands:
Clear Window Vinyl, Auto and Marine Clear Vinyl