The Canon S90 plus waterproof housing runs about $600.

The Ikelite housing for Nikon D-SLR runs about $1500, and Nimar housing with included standard lens port runs about $1200. This will allow you to use a better camera.

If you don't need scuba diving quality waterproof capability, then AquaTech has some pretty good waterproof rain shields that runs about $200 for the Nikon D-SLR.