Not sure this would work, as narcs are seeking energy from you in the form of attention, not giving it to you, so there should be nothing to “return to sender” or reflect back. To deal with narcs you have to ignore them and not let them affect you so you don’t supply them with the attention they are seeking, then they go looking for that energy elsewhere.
If you feel energy is being sent to you though, then a mirror shield would do that. A mirror shield is a normal shield, a bubble around you which you visualise to be mirrored and reflective on the outside, so that any incoming unwanted energy bounces off it back to the sender.
I would recommend employing one permanently as a basic aspect of your personal protections.