I've been using a 2800 mah external charger from monoprice for a week or so. Fits in your pocket and charges fairly quickly for what it is. For the price, I bought a couple of them and keep them in various places in the event I'm not near a charger. Hope this helps - price is definitely right. They also have a great price on cables and the MHL adapter for hdmi.
search for "Micro USB Backup Battery Pack for Smart Phones, Cell Phones and Cameras (2800mAh) - Black (REV. 2.0)"
"Micro USB to HDMI® MHL Adapter - Black"
(sorry, can't post links yet.)