Well, my efforts were not exactly a success. First leather I tried cracked at the fold for the pin. I then tried kangaroo leather as it is thin and tough, unfortunately it is still too thick, next I tried some chrome-tan as it's thinner but two different types proved to be too soft at the fold. I finally got a piece to stay in place around the pin but it has too much stretch to use as a watchband, I don't think buckle holes will last long.
The problem, I finally realised, is the watch, it has recessed parts in the body where the pin/strap fits which severely limits the thickness of the band material. Probably why they use synthetics for all the bands for these I guess. Ah well, it was an interesting experiment. As I have a strap hanging off one side of the watch I'll use it as a fob/pocket watch instead.
Me hats off to you, Jim of Calgary.