Real diving or swimming: Go for those new Tropic straps that look just like the vintage ones but use modern materials. If you google them I think you can find their website easy enough. Desk diving: Try an Italian suede strap either in grey or light brown...
I bought this strap form the webshop of a well known American watch blog. Love the vibe given off by the texture and color of the strap. I do realize that it could do with an additional 1 mm of width. Nevertheless, I think it works quite well as it is. ...
...but realized that it would be better for the Deep Sea (in spite of the size). It doesn’t bother me at all, but I get comments everytime I share a picture 😃 ...
the classic tropic rubber, or sand color or olive drab canvas strap from aboen, as mentioned by thegrailwatch. the aged moss green strap like cfnissen has, is also a very nice combo. or you can try some straps from bulang & son: the taupe grey, dark grey ...