The Hagley Museum and Library in Wilmington, Delaware has a fully operating 19th-century machine shop that is full of belts and pulleys of the type you describe. Robert Howard, the Curator of Industry and Technology there, might be able to suggest a source to you. The address is Box 3630, Wilmington, Delaware 19807, phone is 302-658-2400. Good luck with the exhibit; it sounds great! -Lonn Taylor, National Museum of American History ([log in to unmask])