Bulang and Sons have a few options. Not cheap. https://www.bulangandsons.com/catalogsearch/result/?q=newman I haven't seen a Speedmaster on one yet though.
Reviving this thread. I posted mine on instagram a while ago, and I’m sharing it here in case anyone is wondering how it looks like... https://www.instagram.com/p/CRObzACrLcM/?utm_medium=copy_link btw, this was made by Anh Duc of TJC Leather - https://www.tjcleather.com/watch-strap
Aaron Tan of Singapore made this one. I don't have a link anymore, but he should be pretty easy to track down. Edit: I found his email address. If you want it, drop me a PM.