A while back, I asked about film ribbons for 70mm film development and was pointed to a maker, whose data I need to search for but can always search for that thread or, ask the group again for tips about availability.
As to tanks, it just takes some effort to find a suitable container with lid, that can be locked and taped against inversion misadventures.
A large, strong rubber band of two, that'll allow the film and the apron, plus another trip or two around the circumference of the round assembly of package, minus container will keep the roll snug enough with some common sense handling.
Personally, you might find five or six inch plastic pipe, HDPE should be good with same sized OD/ID lids, caps, plugs, etc, in HDPE material.
If you do no mind a project, you could even clean and recycle number two (#2) plastic, which we've discussed above and make a tank yourself, as this material is everywhere, household milk jugs, laundry detergents, Drano, and many other jars and jugs used in everyday life.
Avoid all the other plastics, with the exception of LDPE, it's 'safe' though, just no as strong as HDPE.