For sale: an REI Squirt model kid's backpack. 8.2 liter/500 cubic inches volume, weighs 13.2oz on my scale. Measures 12' from the shoulder strap mounting point to the waist belt. Can use a one liter hydration reservoir/hose which is not included or the outside pockets with water bottles. In excellent clean condition, $20 including US shipping and PayPal fees.

REI description:

Zippered main compartment can carry everything child needs for summer day trips

Zippered front pocket organizer features a key clip and two mesh pockets plus room for smaller essentials such as lip balm and sunscreen

Side mesh pockets provide storage for found treasures, sunglasses or favorite gizmos and gadgets

Padded shoulder straps and a webbing waistbelt allow adjustability

Shoulder straps have a unique hidden sternum strap adjustment system, minimizing external straps and bulk

Includes a 1-liter Nalgene® hydration reservoir with a bite valve that stores in special pocket inside the main compartment [NOT INLCUDED}

Innovative feature directs hydration sip tube out through either shoulder strap with hose guides to keep tube close by

Back panel is lined with highly breathable, moisture-wicking 3D ventilating mesh--raised panels provide a space for moisture to move to

All-angle reflective piping increases child's visibility in low-light condition