Done a bit of googling and searching around here and WUS but haven't been able to find a reliable source for the adapter needed to switch the omega cosmic 2000 diver (ref 166.137) from bracelet to strap option.

The 166.137 on bracelet has an integrated design and to my knowledge can be switch into a different housing. If anyone has a link to the "strap" housing or a photo of it, would greatly appreciate it!

 

Are you certain such a thing exists? I have one of these and I always thought they were only ever intended to be worn with the bracelet.

I do like the nice original bezel on your watch. It looks in better condition than average. I'm less keen on the modern service replacement next to it.

 

I think it does! The dial, case, and crystal pop out of the bracelet housing and can be put in another housing that supports spring bars.

This watch isn't mine, just an example to show how the watch pops comes out of the bracelet housing.