craftgrrl | stenciling onto cardstock?

What is a good material to use for a stencil that will be applied to carstock?

I've seen plenty of posts about using freezer paper to stencil FABRIC...but what about paper? I am mass-producing little anthology books for a writing class that I teach and the cover design is a recycling sign that I would like to stencil on using acrylic paint. (or would making a stamp be easier? if so, how can I use materials that are available around the house, since i am on a very low budget?)

I thought about cutting up a plastic sheet protector to use as a stencil, but that seems kind of flimsy and i'm afraid it might tear while cutting.
i could use a piece of scrap cardstock, i suppose, but i would like the stencil to be waterproof, if possible (since i'm making a bunch of these books and i don't want the edges of the stencil to get soggy after about 5 goes...)

any suggestions would be much appreciated. i'll post the finished result :)