I have a neutered male cat who is in his 11th year now, and as of this year has had trouble keeping his usual dry food down (same stuff he's been eating for years), vomiting it up a couple times per month. No obviously problems at the vet, so we experimented with different food. We tried a couple of wet foods, increased the ones that worked well for him, and it seemed to resolve the issue mostly. Well, it resolved it in that he only eats the wet food now (and has even more trouble stomaching the dry food, now that he eats it rarely). Going exclusively to wet food got rid of the vomiting.
Unfortunately, we still need an option to free-feed him for specific periods, such as unplanned travel or (as is the case now) an upcoming birth of a baby. In short, if we need to quickly leave for more than 24 hours, we obviously can't just dump a couple of cans of wet food out and go "See ya!" On the converse, our apartment uses magnetic key fobs, so we can't just "leave a key for the cat sitter" (coordinating with cat sitters is quite complicated where we live).
This leaves us needing some other type of emergency free-feeding option that can cover up to 48 hours, but that he can stomach. Are there any specialized dry foods, food dispensers, or highly-spoilproof wet foods that people would recommend for this purpose?