Naptime Shopping

I've found the quickest, easiest shopping trips usually don't include my youngest child-almost 2-years-old. If at all possible I run my errands while someone else is watching him. Other times, I do my shopping during my son's naptime. I know he'll fall asleep in the car and stay asleep once in the stroller.
The only problem is if it's a big shopping trip-like Christmas shopping. How do I push a cart and a stroller?
Well, during my last holiday errand run, I put the umbrella stroller inside the shopping cart, locked the wheels and placed my darling, sleeping son in the stroller and strapped him in. I had plenty of room to place items in the cart and didn't have to fight through crowds while maneuvering a cart and stroller.
(I shopped for an hour and half and he didn't wake up until we were back in the car on the way home!)