That's "bag," that is.
In an effort to reduce the number of plastic bags that enter my house, I've bought 4 reusable bags from http://www.reusablebags.com/. They're the size of a paper bag, will stand up when empty; they're washable and sturdy. They're made out of cordova nylon, like a backback and have a pocket on the side. And they stand up nicely in the back of the minivan, not tipping over and spilling their contents. They're not quite as nice as the ones Mom bought years ago but we've never seen anything like those and I think these are lighter and fold up smaller.
I took them to Target and Publix today and it went pretty well. I got everything in these 4 bags, which means fewer trips out to the car to bring everything in. The cashiers looked at bit askance at them but managed okay. It was better when I bagged my own groceries at Publix. The Target guy was a dweeb. Publix actually has little green reusable bags they're selling but they're too small and not washable.
There are many, many different kinds of bags on the website so you can find what works for you.