I use a number of Pelican Micro Cases.
www.pelican.com/cases/cases.htmlThe 1030 model is similar dimentions to what you are looking for.
They are one tough little case.
The other tough waterproof cases I use are Ultimate Survival cases. They are made by Otterbox and rebadged as Ultimate Survival. I cant see any sized as close to what you want as the Pelican Micro Case though.
www.otterbox.com