I had originally assumed a Fresnel lens would be too hard to make work, but I decided to give it a shot, anyway. I grabbed a cross section from wikipedia and made a surface of revolution from it.
It functioned quite similarly to the plano-convex lens - exactly as advertised.
I nudged the light source closer and farther until the beam looked fairly parallel. No calculations involved.
Here is the Maya / Maxwell file
Here is the lens in .obj format