The best available battery pack for your Gopro hero 3 is Wasabi power battery.
The cells have firmware v1.55 and v01.57. There are further updates also. There are two batteries and a charger with the capability to charge three batteries simultaneously. The battery is LI-ION with the capacity of 1220mAh.
Three years warranty and a welcome bonus is also part of the deal. It is available on Amazon, and you can buy it on other online stores worldwide.