I have used something like this for years: http://www.amazon.com/Folding-Shopping-Double-Basket-Capacity/dp/B0000UZ58C http://www.amazon.com/Folding-Shopping-Do

I have used something like this for years: http://www.amazon.com/Folding-Shopping-Double-Basket-Capacity/dp/B0000UZ58C http://www.amazon.com/Folding-Shopping-Double-Basket-Capacit... It doesn't let you check out from within the cart itself (is that really necessary? If that is what you need, why not just create an app like the Apple Store has?), but it does let you use the same cart both in and outside the store. I bought mine since it makes it a lot easier to walk my groceries home.