GearXS via eBay offers the Wry Baby Kids' Stuf Canvas Backpack in four styles for $5.99 with free shipping. That's $3 under our August mention, $34 off, and the lowest total price we could find. It measures approximately 12" x 9" x 5" and features a side water bottle pouch and padded adjustable straps.
Sunny Sports offers the Marmot Kids' Half Hitch Backpack in Plum Rose for $19.95 plus $6 for shipping. That's the lowest total price we could find by $3. It features a front organizer pocket, mesh outer pockets, reflective accents, and adjustable straps.