I'd like to be able to go to a grocery (or some other) store on my commute from work. I've got a rear rack (b-tween). I know, that I can permanently mount a basket on it, but I'd prefer not to since it makes noise, can be too wide and so on (and looks uncool for me, yes).
So, are there any folding baskets or some alternatives to use?
edit The accepted answer is not about baskets, that's true, but it really about a thing I needed.
To clarify: I want something that I can fold and put inside my backpack (not a big one) and unfold when needed.