Recently someone was looking for a rotating mat, I found a website today that has 14 x 14 mat (Friskars brand) for less than $ 30.00 ( plus shipping, about 10.00) I don't remember seeing this size in the store. But if you find it at Joann's, with the 40% coupon plus the 15% off your total purchase this week, you'll probably come out ahead
This is the quote from the website:
http://www.cutratecrafts.com/product.php/sku/085317
OverviewFISKARS-Cutting mat rotates 360 degrees to easily trim all 4 sides of a block without repositioning fabric. Promotes safe handling of the rotary cutter
-no awkward cuts. Self-healing cutting surface with easy-to-read graphics. 14 x14 size makes squaring 12-1/2 square blocks easy. Comes with its own re-usable storage bag with handles.