What is it that you like about a tub and don't like about a display cage? Is it because you know how to provide the right temps and humidity in a tub and you're afraid you won't be able to in a PVC or wood enclosure? Because it sounds like a display cage of some kind is what you really want.

If you poke around the DIY forum there are a few posts where people have converted things like bookcases, shelves, armoires, etc, into some really impressive and gorgeous enclosures. It does not mean compromising on temperatures and humidity in the slightest, it just requires a slightly different setup. But there are lots of threads that tell you how to do that, too.