You can purchase a manufactured set online. I found this link at Amazon -
http://www.amazon.com/Quilters-Desig.../dp/1571207996 They are called Quilters Design Mirrors. I went the much cheaper route and went to Hobby Lobby and got 2 mirrors for less than $4.00 (they were packaged together and are roughly 2.5 x 4"... set them up with my 60* triangle and duct taped them at that angle. They aren't so pretty but they do get the job done! Good Luck.