They are manufactured by Laptop Lunches. As you can see here, the box comes with a carry case, into which you can slip a cold pack (I've never bothered, because I can use the refrigerator at work. You can order them through the link above, but check with your local co-op first to see if they carry it. I got mine at a local co-op for half the price that they charge at the website.

Once you have it, you can get a lot of ideas of how to fill it at the Laptop Lunchbox Flickr group.