Sunhiker via Amazon offers the Sunhiker Cycling Hiking Water Resistant Travel Backpack in Black for $26.99. Coupon code "PZSJL46S" cuts the price to $19.16 $21.05. With free shipping, that's the lowest price we could find by $10. It features water resistant, tear-resistant nylon, mesh shoulder straps, and bottle holders on either side. Deal ends December 11.

Note: It's available in several other colors for $21.83 with free shipping via the same coupon code.