One for the USA only and available in Black or White for $99 you can order direct from the Apple Store.
For those looking to add a bit more extra battery life to your device the Smart Case, officially designed by Apple nets you:
- Internet use up to 18 hours on LTE*
- Video playback up to 20 hours*
One noticable feature that only would perhaps be available on an Apple smart case:
With the Smart Battery Case on, the intelligent battery status is displayed on the iPhone Lock screen and in Notification Center, so you know exactly how much charge you have left.
If you fancy something a little less bank balance breaking and with similar design aesthetics then try the PowerSkin Shockproof 1500mAh Battery Case Cover with Lightning Connector.