Here's what I used: http://www.edmundoptics.com/optics/optical-lenses/ball-condenser-lenses/n-bk7-ball-lenses/2041 http://www.edmundoptics.com/optics/optical-le

Here's what I used: http://www.edmundoptics.com/optics/optical-lenses/ball-condenser-lenses/n-bk7-ball-lenses/2041 http://www.edmundoptics.com/optics/optical-lenses/ball-conde... Basically, I took a piece of rubber, poked a hole in it, and fit the lens in. It took a couple of hours to get the positioning right but after that it worked like a charm :)