Keystone West via Amazon offers the Lenmar Maven 3,000mAh Battery-Powered Case for iPhone 6 in four colors (Black pictured), model no. BC6, for $29.99. Coupon code "SDLENBC6" cuts the price to $19.99. With free shipping, that's $10 under our August mention and the lowest total price we've seen. (It's a current low by $13, excluding other Amazon vendors.) It provides a 110% charge, effectively doubling the battery life of your device.