Definately bringing back this post from the dead, but I found a container that matches my "requirements".
It is a 37" Work Bin with Wheels from Contico. In the Grainger catalog, it is catalog number 1RG79, the Contico model number is UK3725W. The deminsions are 37"x21"x20". The price is about $60, and weighs 33lbs for shipping.
It features 1" thick rubber wheels (about 3 - 4" in diameter) with ball bearing hubs. Molded-in lockable hasp
Does not appear to be waterproof, but for what I was going to use it for, not an issue.