Interesting this came up... I had the same issue a few weeks ago. I had a short in my headlight bucket, burnt up the harness and the light switch. Due to the poor quality and expense of a reproduction light switch, I recreated the washer/ insulator.
I drew it on Solidworks and 3D printed it. Didn't come out perfect but with come slight modification, it worked! The switch is installed in the car and working.
If you would like the CAD model or for me to send you one, send me a PM.
Check with Sacramento Vintage. They build their own wiring harnesses for the Model A and may be able to assist you.
Interesting this came up... I had the same issue a few weeks ago. I had a short in my headlight bucket, burnt up the harness and the light switch.