Parabolic dishes and you!

After seeing the awesomeness that is , I was inspired to create my own solar death ray. As I was looking around for ways to create it, my favorite way was to use the extra-large dish found at and filling it up with mirrors, because I had extra cardboard boxes lying around at the time to spare. However, the 100-ish 2x2 mirrors that I can fit on it are not enough. Thus, I came to the SDMB to ask this:

Where can one find a program that would create a parabolic arc in stencils that could fit onto printer paper? Or, for that matter, is there a particularly foolproof way that one can further create stencils by hand? I’m aware that a parabola is equidistant sections between a point and a line, but I can’t really think of a way to do that large-scale and easily. Can any of you supply me with any ideas?