I shoulda read more carefully. I just posted on how to replace a panel on the rear jalousie...which 71's and some'72's dont have.
Panels of Lexan are obtainable at glass & window companies. They custom cut. Lexan is unbreakable but can be cut and shaped to fit. Your old window would be the template. Also look for "Plastic Welding" in the yellow pages or Kijiji I suspect your window is "Perspex" or similar and could be repaired and polished.
Me...I'd go for the Lexan. Especially for the front if you have no gravel guard.
Good luck with the repair.
FWIW, I almost bought an early Trill at an auction two years back...serial # 600 or thereabouts, but it looked like a LOT of work to restore. Yours looks awesome
Cheers from "down the 401"