CyberPCs via eBay offers the Dicota Challenge Laptop Backpack, model no. N23919P, for $26.99 with free shipping. That's the lowest total price we could find by $8. It features internal mesh pockets and two side pockets.
AltaTac via eBay offers the Dell 15.6" Leather Laptop Case, model no. ONT355US, for $25.99 with free shipping. That's $4 under our May mention, $64 below list, and the lowest total price we've seen. It fits laptops with up to 15.6" screen and includes an adjustable shoulder strap.