Dan Wenz wrote:

Does anyone know of a source of the Kodak type boxes?

I don't know exactly what size you need, but Light Impressions offers
some slide storage boxes that will hold up to 80 2X2 slides. Perhaps
they would do the trick?

An alternative is to find a local photo shop that processes E6
in-house. I get work done locally, and they return the slides in boxes
similar to Kodak's, but generic white in color. Perhaps such a store
might be able to obtain what you need?