Festool interface pads and the domino tenon set are the two items in my uk bag at the moment since the price difference is large. I paid $200 for my tenon set.
You can get most of the accessories in the states what you cant get but i recommend
Module for the TS 75, Jig saw module, side extension table, CS 70 fence, toolies, PDC drill (I love that thing gotta get me one), pig tail.
Now what to bring- wood peckers squares the small one and the 1281 square, the story stick straight edge, mohawk finishes wood repair sticks especially the expoxy ones and of their larger kits, their butane torch for blending and cutting the crayons.
You can do quite a bit of horse trading with those items, especially the wood peckers