The original crystal is one piece, the cyclops is part of the crystal.
You can use the T19 for the no cyclops look.... or better yet, a T38..if you can find and afford one

. The good news is Clark's are so cheap to just buy a new crystal if you go the sanding route. There is no sapphire for a 1680 and it would look wrong for a vintage Rolex. I know they have conversions for the small DJ's, precisions etc, but on a full size sub not so good. The way the sapphire is held in is different construction too. I'm not big on the cyclops myself, that's problably why the 1680 is the only Rolex sports model I don't own or haven't owned.. lol.
I think you'll be happiest with a low service version T19 in your watch.