There is actually a pretty long thread on different front grill stone protection mods for the 3rd generation Ody. However, the potential for serious damage to the A/C condenser due to stones is not limited to this generation.
Therefore I picked up some gutter guard (aluminum mesh) and some longer (thin) cable binders from the Home Depot and got to work.
I simply cut the mesh to size and then tied it from behind to the existing black grill. I didn't remove the bumper but I had to open the connections between the bumper and the undercover for the engine compartment. That was just enough space to fit in a hand to work with the cable binders from behind.
The mod is probably not strong enough to totally protect from bigger stones but it will hopefully slow them down and therefore limit the damage to the A/C condenser behind.