I would definitely keep an eye on craigslist. I've seen a couple on there in my city. As far as buying one new, they're obviously made, but I don't have the first clue who makes them. Have you checked with Glass Cages to see if they make them? I know this is no help, but have you asked any store owners in your area where they got theirs?
"What, exactly, is the internet? Basically it is a global network exchanging digitized data in such a way that any computer, anywhere, that is equipped with a device called a 'modem', can make a noise like a duck choking on a kazoo." - Dave Barry