I have one as well... An extra battery and external charger is the first thing I buy with each phone. I do wish it was like the external charger for the Fascinate though. It was super slim and doubled as a battery holder and stand for the phone when I travel.
The VZW stores carry them. It comes with an extra standard battery too. You can charge the spare, and it also has a mini USB dongle so you can charge the Bionic at the same time (great for overnight charges while traveling)