that washer is no longer available. But you may be able to repair it with epoxy. Clean it well with lacquer thinner or similar material.
apply glue and let it dry on a completely flat surface. make sure the face next to the impeller is completely smooth and flat.
or you could try getting one from a parts motor.
this part breaks when installed improperly and a lot of them are broken,
there is only one correct orientation for reassembly out of four possible ones. so you have to find the correct orientation before reassembly.
there is no gasket beneath it