I can't help with any bits, but hopefully the following will help your search:
Ignitions are common to 125X, D and E, and probably the YZ100C~H.
Gearboxes are common to D, E and F. The DT and IT gearboxes go in, but are shitty wide ratio things that will slow you down.
Crank cases are common to YZ125D~F, all monoshock DT125/175, and the IT125/175s with the chain on the left.
Actually, I lie: I do have some spare DT cases. Wrong engine number, but clearly the right part even for picky scrutineers (they have 1W1 cast into them, etc).
PM me if you're interested. Cheap.