I wonder if a bit of soda can would work. It is easily cut and could be molded as needed. Pins might go through.
I have a very old domestic treadle coffin top machine. It has a rag around it and I am hesitant to remove it even to clean the machine. Seems to give it caricature and personality. My great grandmother had a similar machine that a cousin now has, so when I look at mine, I think of her sewing for her family.
I also have a 99 Singer with terrible pin scars. It was froze up when I got it, box falling apart and packed full of lint. With lots of loving care I brought her/him back to life and it sews well!! I call it my little giant. I just wish it could tell me all it sewed and for who. I am sure there would be a interesting and fascinating story if it could only tell. It is a knee controlled portable and I found a knee bar that works and the control still works.
Ethel