If you want to do it yourself:
Go to the dealer or any of the wholesale parts sites for part #11009-1872 (GASKET, CLUTCH COVER)
Buy more oil.
Read this multiple times, execute.
https://www.ninjette.org/forums/showthread.php?t=25301
Replacement clutch friction discs: KG Powersports #KG252-5HPK
Replacement clutch steels: Barnett #401-35-078002
INSPECT ORIGINALS BEFORE ORDERING FRICTION/CLUTCH PLATES