I purchased the following USB battery charger device.
http://www.ebay.ca/itm/270810499131. While it doesn't charge the Vox it does keep the battery from discharging. It lasts about 12 hours with a combination of browsing the web, watching videos and being in sleep mode with Wifi enabled.
It takes about 10 hours to charge it from a 500 ma laptop USB power supply.
(I let my Vox go down to 60% of battery life. Then I plugged in this device for the next 12 hours and the Vox battery did not go down at all for the next 12 hours. Even though it stated discharging)
And, of course, you can use it to charge any USB device such as a camera. I can see this being handy for folks who take a lot of photos to carry this device and charge the battery while walking about. Of course folks could just carry a spare battery or two.
Note 1) that it uses 18650 batteries and not AA batteries like I had initially thought. As I'd never heard of 18650 format batteries before I just ignored the mention of 18650 in the eBay item. Also it doesn't explicitly state that 18650 is a battery type. (Except buried way down in the text.)
Note 2) it uses a USB mini port to charge the batteries. The Vox comes with a USB micro charger end so if you do want to charge it at the 2A rate you'll need a USB micro female to USB mini male adapter of some sort.
Note 3) mine at least did not display a red LED when the batteries were getting too low to keep the Vox going. Instead the very bright green LED just stopped glowing which was useful enough.