I've got a 10" Senecca Star lathe that didn't come with a belt.

I read through many old posts on putting belts on lathes, but I
couldn't find anything definitive on what width belt to use. The
pulleys are 1 1/8" wide. One post mentioned that there should be
1/4" on each side, but that would leave only a 5/8" belt and that
doesn't seem very wide. Would a 3/4" - 1" belt work better?

I was planning on purchasing leather from McMaster and skiving
it, but I saw that they had NBR and SBR synthetic belts already
premade in the size I need. Would these be better than leather?