Don't know if they'll help, but here's a couple links that may give you some ideas...
http://www.whitearmor.net/forum/topic/23538-attaching-lenses/
http://www.whitearmor.net/forum/topic/14974-how-to-install-a-green-lens-in-a-stormtrooper-helmet/
http://www.whitearmor.net/forum/topic/10429-how-do-i-attach-flat-green-lenses/