Most important would be non-perishables and water. If there're any waterproof clothes, too - even anything that'll keep warm. Some extra tools just in case, too.
[It's a list as much as it is advice, really. There might not be everything in any of these shops, but he's willing to get as much as they can take, really. Looking over them all wet, there's another thought just then.] Er, maybe medicine if you see any.