Not sure if anyone can offer a better option, but you can try Sea & Sea or Ikelite for one. However, unless they actually offer different housings for film vs digital, be prepared to pay way more than you might expect. Typically, they charge way more for their housing for a particular camera body than the camera body itself. So for the Digital Rebel, it might be ~$1.5K. For my Nikon D70, I believe Sea & Sea has one for ~$2K. And that's just for the body itself, not the lens, external flash, etc.
Check out your most likely options over at B&H's site:
I'm have the same level of knowledge, but you can also check Ewa Marine products. These aren't hard housings but heavy duty bags that are sized for types of cameras. May be cheaper than getting a specific housing for a specific model.
Thanks, folks. Looks like I'd be farther ahead buying a whole unit designed for underwater photography. I know there are housings for Canon digital cameras that are in the 300 dollar range, and a good 5 mp camera can be had for about 500 - so that's a whole lot cheaper than some of the options I'm seeing. Thanks again.