1990 Prelude syncros and bearings no one seems to sell. Syncrotech does not seem anything for this years transmission.

Have the main transmission bearings for prelude 2.0L SI just been discontinued ?

 

Transmission wise, all bastard b parts are discontinued for years.
I always recommend swapping to the H22 or B-Series swaps these days.

Or you can just go to a trasmission repair shop and ask them who they source their parts from for that specific transmission.
But they might not tell you or they will more than likely tell you that all parts are discontiuned.