I have a 70's or 80's Soma(from Japan, not San Fran) Generation with a 1 inch threaded headset, or so I thought it was a one inch threaded headset. I bought a quill stem that is 22.2 diameter and when I tried to put it in it's too big. I was under the impression that that's as small as they get.

Any suggestions on something smaller that will definitely work? I'm assuming I'll have to go vintage and search by trial and error, which is going to be a pain in the ass.