Oil cooler and radiator guards, the OP's question.
They do not need to be heavy or heavy duty, that's for sure. In fact a lightweight plastic honeycomb would do providing the heat did not get to it. Some of them cable tie into position they are so light, though I am not a great fan of using that method, if only out of aesthetics. To give you an idea, Evotech's radiator guard is shown as 420 grammes and the separate oil cooler guard at 180 grammes.
Unfortunately I am not at home at the moment or I could post you one from R&G to show you what they are like.
Point taken, weight is everything on this type of bike. I`ll try ali (but I can see problems with that) and very thin stainless (problems with that too!) and see what the lads think...............