Anyone happen to have an old seat lying around that one of these could be salvaged off of, or just happen (by some odd luck) to have one sitting in a drawer somewhere? Back in the summer when I was having problems with fouling plugs and had my seat off, I realized I was missing one. Maybe that could be causing some un-noticed vibration, and one of the reasons my tailbone kills me sometimes after long rides. If not, I'm going to see if the local "stealer" can get me one, at whatever outrageous cost I'm sure it would be at.
(#3 in the pictures)