Found a nice (smallish) 6-drawered storage cabinet on casters at Ikea: the Helmer, for $39.95. It is thin metal, so will take magnets - probably best for housing smaller (lighter) items...

DD is excited about collecting all her various rocks and trinkets into this cabinet that she can roll around our ground floor... problem is we may need more soon!

http://www.ikea.com/us/en/catalog/products/40107872

Thanks for the info :-) We use similar plastic storage containers that have numerous shelves that house all of DS7's rocks, coins, cards, stamps...you name it....I LOVE the Ikea one on casters though - thanks!