the o rings are part number: 91319-323-000 (o ring, 6x3)
the top washer is part number: 90425-300-000 (washer, 11mm)- a washer like the 6 under the cylinder cover screws
the bottom washer is part number: 90485-001-000 (washer, 6.5mm)- an aluminium crush washer
Mine started leaking slightly from under the crush washer - i tried flattening out the L bracket and annealing the washer but that made the leak worse. So I borrowed the bracket and crush washer from my 550 - still pissed oil out once hot. Then I simply cranked the bolt down just slightly tighter and now the leak is gone!!
John