I hear ya on the seat post. I have a classic Syncro seatpost that I am having sort of the same issue with.
Three options that I can think of (from most expensive to least):
1) Get a Burley Piccolo, it uses a rack attachment instead of the seatpost. The Piccolo rides better than any other TAB I have ridden with or seen.
2) Get a sacrificial seatpost. Save the Thompson for post TAB riding.
3) Instead of having a bushing or gasket machined, make your own from an old inner tube.
#1 may not be expensive as it sounds. You should be able to get good money on resale of the Piccolo.