Quote Originally Posted by XJ35S View Post
I have a machine that takes a flat rubber belt and they don't exist anymore. Tried and failed making a replacement. I Hope to swap it to a pully system some day...
May not work out, but try a vacuum cleaner repair place, auto parts store, or even McMaster Carr for that flat belt. There's nothing new under the sun and it's pretty rare, even for old stuff, that the belts differ significantly from commercially available stuff today. It may not say Singer or whatever, but those things are usually standard sizes and widths. Good luck! I love seeing the old girls still up and running.