I have one of those for school, you can buy them at just about any large "Target-like" store. I think I got mine at Bed Bath and Beyond. I like the size and it could be useful. The only thing I would say is that I couldn't figure out how to fold it back up (I needed to bring it back to school in a VERY full bag) and neither could the 3 other people who tried. I would make sure you know how to do that before you take up the space in your pack!
But I'm sure you would all be much better at figuring it out than we were.