PoweraddDirect via Amazon offers the Poweradd 7-watt Foldable Portable Solar Charger for $35.99. Coupon code "4THJULY2" cuts it to $27.99. With free shipping, that's the lowest total price we could find by $2. (Most merchants charge $68 or more.) It has up to an 18% solar conversion rate, providing up to 5 volts of output and is compatible with most smartphones, tablets, cameras, and other devices that can charge from a 5V adapter.