I can see going to the dollar store & maybe finding little compartmental containers in the stationary aisle (like for pens, paper clips, etc.) that would work inside a Gladware lunch container.
Be careful of things that aren't "food grade" or aren't known to be safe for food. I think you're on the right track, though.
I bought stuff from here: http://stores.ebay.com/The-Bento-Store