Hello Tim, I made one from stainless steel mesh purchased from a local metal dealer for around £8 (this was a good few years ago and had enough to make two) My reason for this extra protection was that returning from a holiday in Spain in the Morgan and we had just entered France when a car in front picked up a flattened can which flew up into the air and came bouncing down the road heading towards our car. By pure luck it missed the radiator and went under the car. However it could have destroyed the radiator.
I made a cardboard template to obtain a good fit then cut out the mesh using a grinder with a cutting disc after marking the mesh with a black marker pen. It took a little time to get it right but the peace of mind of giving the radiator some extra protection was worth the effort. Yes to purchase a new grill is expensive but to have one fitted for the extra protection is for me worth it. We were a long way from home when this happened.
Dinko