An adapter for a support enclosure bin for a roll of thermoplastic bags is described. The bin has a half round cylindrical wall, first and second vertical side walls attached to a supporting rim. The rim has spaced apertures for mounting the bin to a surface that has an opening that permits passage of outer surfaces of the walls but not the rim. The side walls have integral channels that provide support for a rod for a wide roll of bags. The adapter includes first and second bag dispensers for vertically folded coreless roll mounted bags. Each of the dispensers has first and second side panels that are attached together with a connecting link that aligns the front edges and bottom edges of the dispensers. First and second axles are mounted adjacent the outer side panels of the dispensers with positioning wheels that engage the integral channels of the bin.