You mentioned on the vintage machine shop thread that you saw a buttonhole attachment, but did not get it because the machine is straight stitch only. You might want to re-think this. The buttonhole attachment for many of these machines provides the needed motion - I do not know all the ins and outs, but I remember making clothes in my mother's straight stitch machine. When it came time for the buttonholes, she put the attachment on, and zipped through the process. Made the nicest buttonholes. No new machine has been able to match the buttonholes made by that attachment.
As to what feet fit your machine, I am afraid I am no help. Did Charlee or Billy respond to your question?