A Certain Type of Binders (Southern San Rafael)

I'm a music teacher, looking for a specific type of binders for my piano students. They need to be one-and-a-half-inch solid (not flimsy) binders with the rings mounted on the spine (not on the back), clean and in great condition. They also have to be able to be folded back so they can be placed on a piano stand with the rings toward the ceiling. If you can help me with this request, please let me know.