From the money I received for my birthday I decided to buy a sensible product: bicycle bags! This is the way Dutch women get groceries. Not the weekly ones, where you buy liters and liters of milk, but the odds and ends that you forget and have to run to the store for. Some people don't have a car; they use them for everything.
As you can see the bags have zippers. That way, when I have a lot of things to carry with me, I can enlarge the bags. The elastic bands across the bags also hold a box or purse in place.