2011io000oi via eBay offers the GSH 7-Liter Men's Military Shoulder Bag in A-TACS Arid from $7.99 with free shipping. (Other colors are a buck more.) That's a buck below our September mention and the lowest price we could find today by $5. This waterproof bag features a ventilated back panel, an adjustable sling strap, and several pockets.
You very likely are putting your laptop battery into an early grave.