PoweraddDirect via Amazon offers the Poweradd Apollo Solar Panel 7,200mAh External Battery Pack in Black for $27.99. Coupon code "SNY7FCIG" cuts it to $17.99. Plus, Prime members qualify for free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping adds $6.98.) That's the lowest total price we could find by $20. It features solar technology and is compatible with most 5V USB-charged devices.