Rucksack?

I use bags. The Costco ones are very big . Shopping trolleys provided by the stores mean you don’t have to actually carry anything, just wheel it to the car and unload then take the trolley back to the designated place in the car park. They don’t mind you using them here even if you don’t actually shop at that particular store. Probably if we lived right in the city they wouldn’t let you do that.

I had a wonderful shopping trolley which held a week's shopping and was very easy to use. I just held it behind me as I walked, you'd hardly notice it was there. Obviously can also be used for just a few items. Can easily be dragged up stairs. It was great.
Hoppa Shopping Trolley