NeweggFlash offers the RAVPower Element 10,400mAh Power Bank Battery Pack in White, model no. RP-PB07, for $20.99 with free shipping. (Sunvalleytek via Amazon has it in Black for the same price for Prime members.) That ties last week's mention as the best price we've seen. (It's also a current price low by $5.) It features 1-amp and 2.1-amp USB outputs.