Old Ikelite rings had that problem. I think they sitll sell sets of narrow neoprene strips with sticky on on side. Came it three thicknesses. You were supposed to put them on the rings and then tighten down the ring screw. Those might do like Jack has suggested?
Since the Nauticam is without the ring scew, I think you could put them on lens barrel. same as Jack hoping they will stay stuck?
Though I do like the set screws that Stingray used.