When a business sells musical instrments, then later closes, what do the people who have purchased instruments do to purchase necessary parts?

Vibraharp (now some call it a vibraphone) purchased before1970 from the  G. C. Jenkins Company, JenCo Musical Instruments.  They are no longer in business.

Instrument is like a mirimba but the bars are metal and it is electric and played with  hard foam or hard rubber mallets.  Belt needed about 7 3/4 inches long and it is double like a hugh black rubber band and it must stretch to go around the two moveable wheels at the top and down to another wheel about 7 inches below.

If anyone knows where to purchase such a belt, it would be greatly appreciated.  Ebay bethreading1211