Link me to a few?
http://www.amazon.com/VicTsing-Magn...F8&qid=1414022827&sr=8-1&keywords=iphone+lens
http://www.amazon.com/NEEWER®-Angle...F8&qid=1414022827&sr=8-2&keywords=iphone+lens
Dozens more in all shapes and sizes. I have a friend who got the magnetic kind, and they're pretty good actually.
As an Amazon Associate, MacRumors earns a commission from qualifying purchases made through links in this post.