Snap/metal ring to be used for papers
One can attach papers together with a metal ring as on the color selector from a paint producer on the figure. The metal ring is a bit like a snap fastener used for clothes, except it often has a hole in the middle. They probably would come in two pieces that interlock. Does anyone know what those small metal rings are called? What type of store might carry them? I'm at a total loss, even after way-too-long web searches!