Amazon offers Prime members the Fast Forward Girls' Sofia The First Roller Backpack for $8.28 with free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, shipping costs $5.48.) That's the lowest total price we could find by $4. It includes padded shoulder straps and two compartments.
Amazon offers Prime members the Trailmaker Boys' Monkey Face Backpack for $8.18 with free shipping. That's $17 off and the lowest total price we could find. It includes a front pocket and a top handle.