The #115 869 01 21 is a complete assembly with the rubber balloon and the metal brackets. I installed one about two years ago. It is not exactly the same as the original, but it mounts and performs the same. I believe the original rubber balloon showed through the top metal piece that had a hole in it. The new top piece completely covers the balloon.
I am pretty sure that the original rubber balloon is NLA. Not sure I would want to buy a 40 year old rubber part unless it was for concours and wouldn't get used.
Thanks for the heads up JP!