Dear Judith,
There are always a few cat food and litter varieties at supermarkets. Pet/vet stores too.
One unfortunate thing is that supermarkets and stores here are not great about keeping things in stock. Often they wait for things to run out completely and then order, which means it takes time for certain items to reappear on the shelves. I could go around to the vet shops to hunt for what I want when the supermarkets are out, but I prefer instead to mitigate by buying plenty when things are in stock at the supermarket. That way I have a good stock at home and don’t have to worry…e.g., if it’s not in stock this week I’ll buy double when it is in stock next week. Saves me time.
As for number of cats you are probably fine bringing 4 but I would encourage you to check with the law firm listed in this website’s rolodex to make sure.
Regards,