Not sure which Singer it is - what is the Serial Number?
You can find the belts at almost any sewing machine shop - not sure if Joann's sells them or not. I got mine at the local Sewing Machine repair shop - it cost about $8.00, but that was several years go. Just they are not that expensive. It was leather and rather a pain to push the metal thing thru the leather. At least then I knew what the ahl was for when I found it in a drawer of the machine.