Proker via Amazon offers its Proker Ultra-Slim 3,000mAh Extended Battery Charging Case for iPhone 7 / iPhone 8 in Black for $32.99 $29.99. Coupon code "LEHP9B98" cuts that to $24.74 $22.49. With free shipping, that's $32 off and the lowest price we could find. This TPU case adds just 0.26" thickness to your phone and features a rubber hinge design, built-in magnet, and LED indicators. Deal ends December 28.