So I looked up threaded sleeves for like half an hour and it seems the smallest difference they come in is 4mm. Which makes sense, 2mm is not much room to work with.
Anyway, I sent an email to the company in Germany to see if they could make them in 10mm if we did a group buy. At the end of the day I don't see why it would be a problem for them to make them in 10mm, so we will see what they say.
Will let you guys know.
Also I found out a few of the Nismo gear knobs actually have a 12mm and 10mm hole in them so they fit both shafts, perhaps this was the confusion with some people mentioning a 12mm shaft in a R33.