Sunvalleytek via Amazon offers Prime members the RAVPower 8,400mAh External Backup Battery Pack
in Black or White, model no. RP-PB12B, for $12.99
. Plus, Prime members receive free shipping
. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $6.48.) That's tied with our mention from two weeks ago, $87 off list, and the lowest total price we've seen. It features dual 1-amp and 2-amp USB outputs.