I've been thinking a lot how to make a piece to work as a spacer in between the button box and the thread on the base, but it would be much much easier just to add the spacer between the wheel and the button box. I would cut one or two circular pieces on 1,9 mm DM, for instance, with drilled holes and longer screws. The buttons would stay a bit further await from my reach, but I don't mind.
If I decided to buy a real wheel (would a 35 cm wheel be too much for a T300?) I would buy the adapter and use a disher rim, which is also a fantastic idea.