Buy SOONSUN Frame Mount Extension for GoPro Hero 4 3+ 3 with Screen/Battery Extension - Use with LCD BacPac or Battery Extension - Includes Quick Release Buckle and Thumb Screw Online in
Extended Battery Pack for GoPro HERO4, HERO3+, HERO3 [with Backdoor Housings for HERO4 only] (GP-KPHA) - Walmart.com
Best Buy: GoPro Battery BacPac ABPAK-401
Hands-on with the GoPro Hero 3+ Black Edition: Digital Photography Review