cte wrote:Thank you Jason.  
 
 I found one (with small ribs) that fitted. It came from a set of 50 from eBay.  

  I then came across a junk band and used one of the pins from that as I wasn't that confident with the one from the eBay set. 
Thanks for your reply. It's good to know I am not the only one that has trouble getting them. I visited several vintage watch shops in London and none of them could help. At least there are other options.  

 
 
 It's great to hear that you were able to salvage a pin from a junk band!
This is why it pays to keep a box of vintage parts. I own a beautiful condition mid '70s LED watch that I've never worn because the no longer made 19mm width band was too small for me. 
After taking some measurements, I learned that the removable links on a common sized 20mm width mid '70s LED watch band were made by the same company and exactly the same.
I just added 3 links from the junk band and now it fits me like a glove and retains the original band that's well suited to the case. 


 
 
 Cheers!
Jason