The Tarot T-2D 2-axis gimbal for the GoPro 3 action camera typically comes in kit form. It is a very affordable gimbal available from many RC suppliers and delivers excellent results.
This is a Quick & Easy Manual to build this 2-axis gimbal.
Here's the video menu:
00.15 - What's in the box? 00.53 - The 'instructions'; 01.00 - Tools required; 01.15 - Setting up the anti-vibration mount; 01.55 - Fixing the camera mount, IMU & gimbal controller and attaching the leads; 03.38 - Attaching the camera cradle; 04.53 - Bench test.