Hi Tim -- I seem to recall a vendor listed in our links does a stainless steel version of the metal bumper strips that is supposed to be more durable than the stock item. I may get one of those when I get around to replacing my rear bumper (which, even though I have the bumper, will be a while).
Then again, nobody other than you will ever see it, and I'm guessing rust is not a big problem where you live.