These weren't available before, but they are now. Small cardboard tuckboxes from papermart.com. Largest one is 6 x 6 x 3.5 inches. $1 each, down to 80 cents each if you order more than 100. I'm switching over from the plastic clamshells that I was using for my smaller games with cloth boards.
http://www.papermart.com/Product%20Pages/Product.aspx?GroupID=1103&SubGr...