Doug,
John Sanden used to provide (and may still) premixed paints in flesh tones and neutrals and from him bought a paint box that would store 22 colors in 1" square sections and 8) 3"x1"x1" sections. I will try to find a pic (or check the web site below). The hinged top has a rubber seal and latches tightly. I added several drops of "oil of cloves" to slow drying and this tool served me well when traveling. The additive also suited my wet in wet technique.
I also used it at home because I didn't need to sqeeze out paint each day or watch it harden when not in use. Maybe I'll clean it up and start using it again.
Try:
http://www.jhsanden.com/institute/brochures.htm or:
[email protected]