You could also try some Thermaform. It comes as sheets of thin, clear plastic. Mount your old canopy on the end of a pencil so you have some room beneath it. Heat the Thermaform with a candle, and when it starts to sag pull it down over the old canopy and it will make a new "Copy" of it. Trim it out and you are good to go.
I've never personally used it, but I've seen some posts by people who have and supposedly it works pretty well. It's available through Squadron at www.squadron.com