TomTop offers the Free Knight 50-Liter Outdoor Sport Backpack in several colors (Red pictured) for $15.99 with free shipping. (Choose "Priority Shipping" during checkout.) Excluding the below mention, that's the lowest price we could find today by $6, although we saw it in fewer colors for a buck less in August. This water-resistant pack features multiple exterior pockets, a padded back support, ergonomic padded shoulder straps, and adjustable chest and waist belts. Deal ends October 31.

Note: The countdown timer on the product page does not reflect an actual expiration time and resets daily.

A close price: Yall-Ca via eBay offers it in Camouflage Blue or Camouflage Green for $16.59 with free shipping.