Inspired in part by this thread, I bought a 34 gallon semi-clear PP (Polypropylene) box called "SAMLA" at IKEA for $15; lid and lid snap clip locks extra. It does not appear to be as tough/rugged as the Shelterbox, but I won't be air-dropping this or using a mule to haul it. It is intended to be a family Bug Out Box. I don't know its weight capacity, but it'll hold (both in weight & volume) what I plan to stock it with. It comes with four single direction casters that can be snapped out and made to go either "front & back" or "left & right". See dimensions here, but you have to buy in store:
http://www.ikea.com/us/en/catalog/products/30102974

I'll edit this post once I find the receipt and can give the cost for lid and clip locks.