Rick, I have a treadle saw I use for demonstrating that uses a round leather belt. I happen to live near an Amish community and can get the belting locally, but they are available online (McMaster-Carr is one place I’ve seen). Once you cut the belt to length you connect the two ends with a wire connector. Sometimes you have to use it for a bit, let it stretch, and then snip the end off and reconnect the wire. Not as big a deal as it sounds. They also have hollow core polyurethane belts with quick connectors, but I prefer to use the leather belts to stay as true to original as possible. Here’s their link to give you an idea of options …
https://www.mcmaster.com/round-belts/
This is my ~130 yo beauty