There are many portable chargers for iPhone on the market. If you need a larger capacity portable charger, check out the following one.
Pebble portable charger features a slim design, and measures 9.8 x 7.2 x 1.8 cm. Unlike some portable solar chargers, it comes with a 5000mAh large capacity rechargeable battery. It means that the portable charger can charge your iPhone four times after fully charged. Moreover, it comes with several connectors for other cell phones, including Sony Ericsson, Mini USB, and Nokia.
Pebble portable charger is priced at about $77 USD. You can grab it from Firebox.