I've a great all round condition 2003 A4 Avant and wondering if anyone can recommend the best way to protect the painted rear metal bumper surround just above the lower grey hard plastic one. I know about rear facing cameras for parking etc., but this would be to stop damage from inconsiderate drivers usually with old bangers when I'm not with the car. I've already got a few marks on the rear bumper paint which is really annoying.

I've thought of some hard rubber cushioning but I doubt it would stay in place very long and would soon fall off. Has anyone had the same problem or found a long term workable solution yet.... ?

Thanks