Plusinno via Amazon offers the iPhone 6 Plus 5.5" 2,100mAh Portable Battery Bank Case in Gold or Silver for $25.99. Coupon code "DUS2WFPV" cuts the price to $16.95. Plus, Prime members qualify for free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, it adds $6.03.) That's $20 off and tied with last week's mention as the lowest total price we could find. This ultra-thin battery case gives up to 50% more battery life for your iPhone.