The boards for the different tanks are nto interchangeable. Different physical layout is one thing, but the Tiger/T72 board actually functions differently from the older tanks.
Toyeast is such a great place for VsTank parts because they're owned by the same parent
T72 parts should be available in quanitity in September...but if you really need something, I'd definately email Toyeast and VsTank.
And how did you get your treads to go bald? I run my T72 non stop, and its treads show wear, but nothing close to baldness!
Edit:
And the new Type 90 isn't out yet...It's been getting quietly pushed back for years now. It will be a lot nicer than the old Marui version, whenever it happens to show up. August was the last release date I heard, but that was a long time ago. I'm guessing it will be among the 5 modern tanks released in 09.