Yamaha part numbers: 3D7-15411 COVER, CRANKCASE 1
(BTW, Yamaha always numbers their left/right parts 1 and 2; crankcase covers, levers, etc. , left is 1)
3D7-15451-00-00 GASKET, CRANKCASE COVER
If you want to replace the o rings too:
93210-32800-00 small
93210-14369-00 large
Shouldn't retail for much more than $100.00 for all...It should be possible to repair (JB Weld or similar) if there are not too many pieces missing, cavity not under any pressure. Just watch clearance to flywheel/stator and wires on back side.