We know that DS will only take 30 or so minutes in the trolley/ergo, so we make sure we stop every so often so he can run. We stick to shopping centres with play areas or markets with parks. He HAS to hold our hands when there are cars around, but if he doesn't want to hold hands in a situation we consider safe he gets asked to stay close. He's usually ok with that.

My DS runs when he's bored, or wants to play. So we try to give him opportunities for play and he has a couple of trolley toys for food shopping trips. Maybe think about why your DS is running, and see if you can prevent it? Some people just really hate shopping, and there are definately times I want to run away and play with bark too