Would Mexico be a good source for these? Or Amish / Mennonites?
I’d call Singer up directly and ask. I found a stock of such being sold at Walmart in Aberdeen Md. once for $70 brand new as if just manufactured in 1870 and what had happened was that a bunch of them had missed the boat they were supposed to be on at Baltimore harbor and one of Wallies buyers spotted them and made somebody an offer on the spot. Ask yourself how many countries might there be without reliable electricity, and then the guys out there living in yurts on the steppes still need clothing sewn too. The things are tougher than nails and could easily sew through leather, and heavy.