Buy from Amazon : http://www.amazon.com/gp/product/B00H4IRE5U?tag=scratchandsti-20

GoPro HERO3 Camcorder External Microphone Vidpro XM-L Wired Lavalier microphone - 20' Audio

Vidpro XM-L Wired Lavalier microphone - 20 Audio Cable
Includes lapel clip and foam windscreen
Sensitivity -30dB - 3dB 0dB 1VPa 1kHz
Microphone connects via a 4 long cable with 35mm audio plug
Designed for use with Gopro Hero4 Hero3 Hero3 and Hero2 cameras