Adorable Target shopping bag
Couldn't find a link on target for this, so here is just something about it.
It's way too cute, is a fullsize shopping bag, and zips up very easily into the size of a wallet. They're $1. I'm keeping at least one in my car - this is the sort of thing that one day, you'll curse yourself for not having one on hand, because you need it right then.
They're of a heat-bonded nonwoven polypropylene fabric.