Thanks to a tip in a PM, here is a source for a container for 100' spools of film:

This is how movie film comes packaged when it is on a 100' camera spool. I would worry about the box alone protecting film on a core from light... as they may also be depending on the opaque metal spool and the opaque paper band to complete the lightproofing. But perhaps sealing it with some gaffer's tape would be good enough.

(I'm not going into the 5222 distribution business, remember, so this is for anyone else that might need such an item.)