I have made my own stencils using the Avery Style Clear Plastic Insertable Divider for my plastic. This is strong clear plastic so easy to work with for any type of template.
I got a Olfa Stencil Cutter from JoAnn's. It has 3 double blades in it (1 mm, 1.5 mm, 2 mm), and cuts a line in the plastic those widths. It works surprisingly well. You need to start and stop it when drawing on the line you have drawn on the plastic. It is some work, but you get just the design and size you need. I will enlarge, or shrink the pattern on my printer, then can trace over it onto the plastic. Then easily mark my quilt.
Here is a link to what my blade looks like: http://www.quiltenhobby.nl/Olfa-Sc-1-Stencil-cutter/en