I have a laptop. It is a 17 inch or so and heavy. I bought a case for it when I bought it. Something like $35 for that case. Then after getting and using the laptop, I detested the keyboard and the pad for mouse simulation which I always managed to touch at just the wrong time. So, I bought a wireless keyboard and mouse to use with it. That helped a lot. But, it was tough stuffing laptop, mouse, charger, and keyboard in the original case. It also turned out to be hard on the added keyboard. Soon keys weren't working, etc.
I bought another keyboard and mouse and decided to keep it in the box it came in. But, that and the laptop, etc would not fit in the laptop case or bag. We looked at some for larger laptops, etc., but the prices on anything larger than that for small laptops alone were ridiculously high for a few cents more leather or plastic and a slightly longer zipper. Then while buying groceries I saw those zipper insulated bags for hauling frozen foods home in the hot summer. Hmmmm. Interesting.
Price was only about $7, so I got one. No problem sticking the keyboard, mouse and box in it and the laptop with the original case also went into it. Not the classiest looking case by any means, but it sure does work and the insulation provides a tiny bit more protection for everything. It is easy to carry, but a bit large compared to custom cases. Probably room for a few sandwiches, etc in there as well, but that is probably less than a wonderful idea when another one just for grub and drinks would cost less than half of a wireless mouse at a good sale price.
***Stay tuned even if you would never, ever put a laptop in a case sanitary and insulated for frozen meat and vegetables--- Doug Wiken