I believe there are several different brands of the no-melt, or heat resistant, mylar plastic template sheets. I got mine at Amazon in the 12"x18" size for this. They also come in packs of 6 sheets of 8"x11". I use them for applique shapes too, like all the hearts in my avatar picture.
http://www.amazon.com/EZ-Quilting-88...ef=pd_sim_ac_8
http://www.amazon.com/EZ-Quilting-88...ef=pd_sim_ac_7