I get it. Sounds a lot like expanded metal. I was thinking something like this: http://www.metalsdepot.com/products/hrsteel2.phtml?page=expandedThe idea I thought of to protect a side mount radiator would be to use 1" wide strips of 1/8" steel plate in a grid pattern in front of the radiator with a frame that the radiator would mount to. The steel plate would be arranged so that it would look like a honeycomb structure in front of the radiator, providing the most protection from damage while not impeding airflow. Let me know if that makes sense.
The hardest part to me is figuring out where the line between protection and comprimising air flow is.