I've often thought what a perfect hide a ceramic one would be. Like was said, waterproof, easy to clean, choice of colors to match decor, easy to sanitize, hard to tip over. They'd be ideal in my opinion.
If you make these, put me on the list for a dozen hatchling size, another dozen large cereal bowl size, and a half dozen about 12" across for my big girls.
If I had the means, I'd do this, but kilns are not cheap.
Gale