Where I live (Montréal, Canada) plastic bags are banned everywhere. You either bring your own or buy a reusable at the cash. Some places (like grocery stores) also sell paper bags. You get used to it. If you have a car you leave a bunch of reusables in the trunk, if you don’t you just have to remember to bring one with you. The also sell some super thin ones you can carry in your pockets that are sturdy and large enough for a small run at the grocery store.