TomTop offers the Free Knight 50-Liter Outdoor Sport Backpack in four colors (Yellow pictured) for $15.39 with free shipping. That's the lowest total price we could find by $8.

TomTop also has the Tomshoo 40-Liter Outdoor Foldable Bag in Blue for $13.39 with free shipping. That's the best price we could find by $5.