Plastic cup lid has four buttons, one of the buttons fell off, with what glue can be glued up safe and non-toxic?

This can not be glued, you buy back when the buckle and cover is the whole inverted mold and the material polymerization of linear molecules, which can you thousands of times up and down folding, the current market of universal adhesive polymerization is a mesh structure in principle leads to the brittleness of the universal adhesive, more used to stick some rigid appliances, you can cover this cup of three buckles, but only the aesthetics of the lack of good