I think I will stalk this thread and peruse its links as well... I've been running into the same problem, and my dragon is only 5mo! The breeder said he was big for his age - he was bigger than his clutchmates, minus his lack of tail - and the three petshops I've been to didn't have anything where the opening would fit him now with room to grow, either. Everything was for skinny little serpents or smaller herps, or alternately, enormous.
My little guy is currently sleeping in a cardboard box (as in - one I put together out of cardboard to suit his size, not a shoebox), but in just a month, he's already outgrowing it. =\