I have one reserved, but it hasn't come in yet. Looks like the little coin type thing people use in quilting to give the 1/4" edge for the seam, only in different sizes. I think it will work out great for cut-outs and lettering. Hope its worth the $12 for it.

Read somewhere using round metal washers would work the same way (just buy them in the width you need.) So I picked some up. The hole in the middle was a little too big for the pen, so I tried duct tape on both sides and used a push pin in the center to make a hole big enough for my pen. Seems to work!

It probably doesn't have to be metal. Think of something that's disc shaped... as long as it has a hole in the center -or if you could pierce a hole in it- it could work.

You line up the "outside" of the disc with your picture/item, and as you go around it, the pen/pencil in the center traces out a perfect mat (according to the radius of the width.)
Hopes this makes sense.