I had the same bushing go out on my 82 a year ago.  Yes indeed, it is
located above the fuel tank, so even if you can find a replacement, which
is somewhat doubtful, you will need to drop the fuel tank to get to it.
Sometimes the German engineers get it right, and sometimes they don't.
This would be the latter case.  As a temporary fix, I took a piece of high
density polyethylene plastic(from a kitchen cutting board), drilled a hole
slightly bigger than the shiftrod linkage, cut the piece in half across the
hole, and mounted it where the linkage passes through the bulkhead on the
rearward side of the fuel tank.  the semi-circular hole supports the
shiftrod and is easily accessible for greasing.  This is one of those
temporary fixes that may end up being a permanent fix.

--
Brett in Portland, OR
"Albert" '82 VanaFox I4 Riviera