Walmart has the Ozark Trail 2,400mAh Portable Phone Charger with Solar Panel for $29 with in-store pickup or $5.99 for shipping. Features a 2,400mAh rechargeable battery and eight hour charging time with the solar panel.
Amazon has the X-Dragon 15,000mAh Solar Portable Battery Pack (Blue or Orange) for $24 - $7 off with coupon B3PQ7KKQ = $17 with free shipping on $25+. Has excellent Amazon Reviews.
Amazon has the Pisen 20,000mAh Portable Charger Power (Bank in Black) for $30 - $10 off RT9EH27U = $20 with free shipping. Has excellent Amazon Reviews.
Amazon has the Pisen 20,000mAh Portable Charger Power Bank (Black or White) for $30 - $10 off with coupon RT9EH27U (Ends 12/31) = $20 with free shipping on $25+. Features one micro USB cable, 5V 2A input for quick charging, and a smart digital display LCD screen.
Has excellent Amazon Reviews.