Do you still have this part? It looks exactly like the ones on my 1984 E28+. One of mine just disintegrated. It is (was) 3 1/2" long on each side, 1 3/4" deep, and 2 1/2" tall. I just put out a search on Parts Ferret, too. I attached photos of each side so you can compare yours to mine.
Jeff Olmstead