Amazon.com : GoPro Battery BacPac for Hero3+ : Electronics
Amazon.com : SOONSUN Standard Waterproof Case Dive Housing for GoPro Hero 4 Black, Hero 4 Silver, Hero 3+, Hero 3 Cameras with BacPac Backdoor for Extended Battery or Bacpac Screen – Waterproof Up to 40 Meters : Electronics
AliExpress
Battery or Dual Charger for GoPro Hero 3, Hero 3+ Silver Edition & Black Edition | eBay