can you think of any places where food would be stored apart from shops and supermarkets.
ie oap homes hospitals ferry boats
think out of the box places where joe public wont think of
garages, pubs, cafe's, truck stops, garden centres, farm supply shops, farm shops, sub post offices(small village ones are also the village stores).
Schools. Most schools have two storage spaces for food. So if the kitchen has been emptied already then check outside the kitchen. You may get lucky.
offices,.. most have vending machines,... almost anywhere that people hang about
Also warehouses that supply offices , I worked in one that stocked teabags and the small cartons of long life milk .
Train station,
Some long distant trains still have food on board.
If you acted quickly them fast food chains store masses of chicken and burgers, they also have concentrated soft drinks, coffee, tea, sugar, salt, pepper, ketchup etc.
People would be raiding shops and supermarkets first.
Chip shops for potatoes.
Factory canteens.
Commercial distribution hubs.
I have a massive refrigeration place down the road that stores thousands of tonnes of dairy products for all the major dairy manufactures.
So try and find out what companies are on your local industrial sites.
ships in port will have to feed the crew plus whats in the hull