Accessory Charging extra battry out of the phone with a USB power port???

view story

http://androidforums.com – I have extra batteries for my Prevail. I am looking for a way to charge them when on the road. I need to charge them outside the phone. I did find chargers that plug in to a ac wall socket to charge the phone. But I need to do it though a USB power port so I can charge them when driving on the road. I did see this one on eBay. Desktop Wall US USB Battery Charger Samsung Galaxy Prevail M820 Transform M920 | eBay I did but it. In fact I bought it two times and every time they sent a different unit. Even though in an email exchange they said they would send the right item, and it will (General)