I thought I'd add a note since I solved the problem, at least for now. That bushing would be very hard to source so I decided to use two regular rubber o rings to "fill" the space. I just got a few from the hardware store and they squished in the space when I tightened the bolt down. Seems to hold pretty well, taking up the slack and making the seat feel stable. They may last a while or not. But they aren't hard to change now that I know what is the issue. There is no compromise of safety here because the bolt itself is not going to break if there is an impact or accident.

__________________
DS
2010 CL550 - Heaven help me but it's beautiful
87 300D a labor of love
11 GLK 350 So far, so good
08 E350 4matic, Love it.
99 E320 too rusted, sold
87 260E Donated to Newgate School
www.Newgateschool.org - check it out.
12 Ford Escape, sold, forgotten
87 300D, sold, what a mistake
06 Passat 2.0T, PITA, sold

Las Vegas NV