Casters? Any Ideas?

Near here, there's a place that buys and sells used tools. (http://www.toolsupermarket.com/services Only including the link so you get an idea of what they're about, although, if you want to contact them, that'd be up to you.) Among things I've bought there, were some nice, heavy duty, casters. The guy told me they'd come from some US Postal Service equipment. If you have anyplace like that near you, you could give them a try. Heck, these days, you might even be able to search the internet and find some more places like that, and all you'd have to do is box em up and ship em off.