I happened on this video today, of a :

https://www.youtube.com/watch?v=8yso_QxvbL4

It looks ingenious and probably relatively simple to design & build by anyone with basic building skills (not I). It occurred to me that something like it could be designed on a smaller scale to work with one's backpack or bag, to provide a changing bag for film loading/unloading when traveling. The commercially produced tents are costly (though, yes, a long-term investment, good for those who travel a lot or lack a darkroom at home); changing bags lack a height insert to keep the roof off the holder/film. Light-tight sleeve/cuff openings would still be necessary.

Anyway, just a thought in case someone with skills might run with it and post back ideas.