It's a push pull switch. Korves Oliver ( <!-- w --><a class="postlink" href="http://www.korvesoliver.com">www.korvesoliver.com</a><!-- w --> ) has them, and so does Ag Parts First ( <!-- w --><a class="postlink" href="http://www.agpartsfirst.com">www.agpartsfirst.com</a><!-- w --> ).  Both are good reputable places to buy from.

Ian - If Peckens started in the early 30s, then they beat us by a few years. The earliest sale of an Oliver dad could find from us was in 1937. But my 1955 FWA that I bought 2 years ago came from Peckens!