The ‘easy’ way is to replace broken case parts with those from a ‘dead’ unit. However, if this is not possible, ‘super glue’, cyanoacrylate adhesive bonds well to the plastics used. The parts must be clean and very slightly moist. Breathe on them before applying the glue. Hold the parts together (with sticky tape) and leave unisturbed for as long as possible. Hours rather than minutes! If possible do this in a warm environment.