MBKid

I just finished installing my new water pump (mb#104-200-33-01-88) when I realized there is an extra port for a water line that my 1995 C280 does not use. The port has two threads for 2 screws (one on each side) of the hole and an o-ring. I need a cap or some way to close this port. The attached picture shows an aftermarket pump that already sealed the area I am talking about (the arrows point to the port). I don't have the original water pump so no luck pulling it from there, but I don't even think there was a cap with screws on the original pump. Need help fast as I just need to plug this port.
Thanks, CypressKB@yahoo.com