Emily,
I also own a treadle machine. I purchased it at an antique store. I think I only paid $40. If you have any Amish or Menninite communities within a reasonable distance of you they probably have persons who service such machines. I live just south of Hanover PA. There is a machine dealer there who is a Menninite. He actually services treadle machines. I purchased a new belt from him. He even had it in stock.
I doubt if I will ever use it but it is in working order if the need ever arises.