You may need to get the whole lower box assembly as its likely comes together with that. Or pull one from a salvage yard. It should very likely be the same from 2005 300, Magnum, Charger and up. V6 and up, shouldn't matter, that part of the chassis hasn't changed since then. That other grommet and isolator you see in the diagrams are for the part of the airbox that mounts to the top of the rad support.