M.D.
This is a great post question. I have been looking for these too. I did find at Target a ziploc container that may be of use until you find what you looking for. It is a plastic container, divided into three sections, it fits inside most lunch boxes. I used them last year and they worked out great. I can not find exactly what the particular "ziploc" container is called but you should be able to find it at Target where they keep their ziploc bags etc.