We measured the old ones, cut out new windows with the die grinder, pre-drilled the holes and installed with soft rivets. We cut the strips from bulk material. In Fairbanks, Tamarack Air parts stocks it.
I was a bit paranoid about drilling/riveting plexi, so I glued mine too (Polytak). Nothing has moved or shown signs of separating. Conversely, I loved drilling/screwing the Lexan, can't hurt that stuff.
Oh, one other thing. We found that once we got everything ready, it was easier to install (read "bend" ) the windows to get them into the channels and then install the strips.