You can replace it with using an easy to purchase and cheap replacement lens for the GoPro HD Hero 2.
Try this link; [https://www.google.com/search?q=as100+vs+az1&oq=as100+vs+az1&aqs=chrome..69i57.11620j0j7&sourceid=chrome&es_sm=122&ie=UTF-8#safe=off&q=m12+wide+170+degree+replacement+sport+camera+dv+lens+for+gopro+hero+2]
If that doesn't work, try searching google for a "GoPro Hero 2 replacement lens."