D.M.
How about The Container Store? I found this one online: http://www.containerstore.com/browse/Product.jhtml?CATID=.... It only has two sections but you could buy two and use the removable divider from the second one to make a three-section container.
Another option is to Google "bento" or "bento box". Bento boxes are a neat way to pack lunches. They often have really specialized containers. Good luck!