I don't know if this is what you are looking for but after reading your message I thought what you suggested would be a good idea. I drilled two overlapping holes in each handle of the controller and used a box cutter to open them into a slot so that a small carabiner would hook into the holes. I then tied a loop in each end of a length of parachute cord and clipped one end into each carabiner. I put the cord around my neck and the controller hangs upside down against my belly. I just unclip the carabiners and fold the controller up when I put my equipment away.
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