decor make a great little bento type box. It is one container with 4 compartments.
We often take our 'picnic plate' as Darcy calls it. She has something different in each compartment and feels grown up choosing what she wants.
I pretty much use all of the above suggestions with the inclusion of cold meat pieces and cherry tomatoes, cheerios and sangers cut out with cookie cutters (cool shapes plus they fit more neatly).