Since I'm the OP, my apologies for not giving a bit more background in my original post.
In the old days I'd bring film from home on my international travels and process it on my return. I can safely get unexposed 120 film out of the US thanks to upon-request hand-inspection, but with CT-based carry-on luggage scanners proliferating around the world getting film into some countries or home again without X-ray damage may soon be impossible. This has got me to thinking about what it would take to process film during travel, and secondarily about obtaining 120 film on arrival.
The Ilford darkroom network is useful for those places that have darkrooms, and asking here on Photrio can help in locating stores that still sell film. In fact, I've already been making inquiries in a country to which we hope to travel in late summer and have found two shops in the capital where I can purchase film upon arrival and a darkroom where I can process it before returning home. Unfortunately, there are no darkrooms currently listed in some of the places on my future-travel list and this is why I decided to experiment with Caffenol (there may also be no places to buy film, that's another problem). Also, in many parts of the world personal (or even public) swimming pools are either rare on non-existent so while they may have markets with the ingredients for Caffenol there are no stores selling pool chemicals. And this is the problem that's got me wondering about "supermarket fixer".
In the worst case I could take a pound of Sodium thiosulfate or maybe a small bottle of Ilford Rapid Fix stock (and an HDPE bottle and developing tank and reels and a small graduate and measuring spoons and...) in my luggage and hope that it doesn't get taken away in an act of security theater. I don't mind if I have to refix my film once I arrive home.
I sure wish Ron Mowrey was still with us.