This is what I use, and am very happy with:
Honeycomb Radiator Protector, 19 x 26 Inch
Different sizes available and easy to trim and put in place. I had seen a car with a metal screen like this:
Radiator/Grille Shaker Screen, 31 x 19
mounted in a metal frame and attached to the car with springs so that the screen would 'give' if something large hit it, like tire debris or God knows what off of our roads. I use the mesh and have had no problems.