I was checking out the clearance at this quilt shop and they have a kit to learn quilting for $ 4.50 It includes the companion ruler. Anyone that wants the ruler should check it out. I can't imagine you would find it for much cheaper. Well maybe you can, I have not checked. But here is the addy,
http://www.homesew.com/ClearanceQuilting.html
Scroll down to the bottom of the clearance items.