I've always been able to buy groceries for a whole family while walking (back when going to a supermarket was still normal), what exactly do you see as the major roadblock for something like that? Bring bags or maybe a (large) backpack and some packing skills, you will be fine. You can even take one of those bag on wheels type things if you cannot or will not carry heavy weights - I certainly have if I knew I needed a lot of drinks for a party or something similar.