Short shank Singer buttonholers from that era are easy to find, and they fit the FW. Part #160506 is the common one in the green square plastic case. There are buttonholers from earlier days (that look like a bony dinosaur) and ones that were made a little later, including the Jetson's looking case. As far as I know most of them will fit the FW. The other kind that were made fit slant machines. I believe the slant cases are usually maroon or pink.