I also agree that it is a great game and highly underrated. However, I would assume that two key factors preventing the availability of a reproduction backglass are:

(1) The backglass would be expensive to reproduce especially given that it is has some mirroring

(2) The game has always sold at relatively low prices, so the reproduction backglass would represent a high % of the total game cost

Having said that, though, I'm also one who believes that there would be plenty of folks willing to pay that high % of game cost for a replacement backglass, regardless of what the economics say.