You can easily make your own using Bond Paper( this is the kind which business letters are usually printed on). Simply measure the diameter of the hole in the block, divide by 2 to establish the radius of the hole you'll scribe with your compass, cut it out with either a #10 blade or a scissors, poke holes through your blank after you push the back plate through the big hole, and bolt it tight with your BP screws. Cut the excess off with your knife and fly! The paper is amazingly durable and with the good quality of junk mail paper we get daily you'll have a never ending supply! This process works on all the engines I've ever used over the past 69 years. You may use an all, or a compass' pointy post to make the holes in your blank.