Sunvalleytek via Amazon offers Prime members the RAVPower Element 10,400mAh Power Bank Battery Pack in Black or White, model no. RP-PB07, for $24.99. Coupon code "LCT9QZN3" cuts the price to $19.99. Plus Prime members quality for free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, it adds $6.58.) That's a buck under our mention from two weeks ago and the best price we've seen. (It's a current low by a buck.) It features 1-amp and 2.1-amp USB outputs.