You might check out Pelican cases on Amazon or at the Pelican site.

It looks like the Pelican 1640 transport case would work as well as their larger cube cases. The 1640 looks to go from a bit under $200+ to a bit under $400 depending on the foam inserts and vendor. Pelican is pretty serious gear. Built to last, watertight, etc. This model has built in wheels (double wheels for heavy weight) and handle for transport.