I got a email about the lens I use so I thought I'd post it again. I'm sure this has been mentioned in the past. The way I mount mine is by using velcor on the ends and just curve it on the inside. It works great and makes it easy to remove to clean.
I get mine here.
http://www.motorcycle-superstore.com/1/1/69/11378/ITEM/AFX-Fast-Shield.aspx
Right now only $11.99