A new Pierburg pump is $250-300.

If you don’t mind investing in a gasket, pull the pump and confirm the plastic bearing spacer is intact. If the balls are able to touch each other, keep the car off the road until you get another pump.

If it has a metal gasket, apply some RTV to both sides and reuse it. New Pierburg pumps come with a gasket. I don’t know about Chinese pumps.

Sixto
98 E320s sedan and wagon
02 C320 wagon