I'm really sorry to hear about your rear curtain window. I think every owner of a convertible should relay caution of dropping the top in cold weather to the new owner. Unfortunately I did the same thing with my old Jeep when I first got it. As of a replacement...you can have a local shop that does tops give you a quote and let them do all the work...would guess it would run $300-$400. Or you can order one from a online top company. I found this one off eBay doing a quick search:
http://cgi.ebay.com/ebaymotors...ories
As for a glass window/top replacement...there isn't one. The way the top folds down it bends the rear window so a glass window would break. Think a member here did a custom glass window but it was really small if I remember correctly.
Do a quick search of the vert forum...some of the other member have made a rear window out of clear vinyl and velcro...most of them look really good too. And at a fraction of the cost. Hope this helps. Good luck!