I am surprised that glass companies won't touch it. Are these ones that will do windshields and other automotive glass work, or only residential stuff, or preferably both? Also, have you enquired of the cap maker if you can get replacement glass or a replacement door/window?
The glass was obviously tempered safety glass, as it ought to be (it may well be legally required to be safety glass of some sort). Getting a replacement, if you can't obtain the glass from the cap maker, would involve cutting a piece of untempered flat glass to shape and having it tempered before installation. I would think that most decent glass companies would be capable of this sort of work, though they may well have to sub out the tempering to a specialist company.
Plexiglass or Lexan (polycarbonate) is not a bad idea, as was suggested above.