Thanks Gerald. I was in a bit of a rush so I went to the local hardware store. They didn't have just the washer, but they had a fitting that included the washer so I bought that. The good news is the water bay panel was removed, the leaking drain line was repaired, and the panel was replaced with no left over parts, no supply line leaks, and no bloody fingers. But I have to say, the person that designed that whole area should be taken to the shed. Hope I don't need to do that again any time soon.
