Amazon offers the Lumsing 10,400mAh Portable Power Bank, model no. LUM-008-01, in Black, White, or Champagne for $24.59. Coupon code "TFBCKVPO" drops it to $19.59. Plus, Prime members bag free shipping. (Non-Prime members can spend $35 to qualify for free shipping; otherwise, it adds $6.55.) That's tied with our May mention, $40 off list, and the best deal we've seen for this charger. It's compatible with most smartphones, tablets, and other USB devices.