This is the one I got, but they have much nicer ones now. Similar to the ollo clip, but much less expensive :)

http://www.amazon.com/Magnetic-0-67X-Angle-Designed-iPhone/dp/B005OIGVG0/ref=sr_1_10?ie=UTF8&qid=1391801844&sr=8-10&keywords=iphone+macro+lens