NeweggFlash offers the refurbished Targus 4,800mAh Backup Battery for Mobile Devices, model no. APB27US, for $5.99 with free shipping. That's $4 under our mention of a new one from four days ago and the lowest total price we've seen for this battery. (It's also $12 under the best price we could find for a new one.) This rechargeable unit charges USB devices and features both microUSB and miniUSB ports. Deal ends August 30.
A 90-day warranty applies, although it's unclear who backs it.