Don’t know if these guys can ship to the UK, but claim to be real reps. Doesn’t help with the trying on first part though.
https://timemachineplus.com/collections/buy-mido-watches?page=1
If interested I can dig out a coupon code I was sent from them once that I think was good for %20 off.
Occurs to me that he could be wearing a replica of, or a vintage model, of the watch that Oppenheimer wore, as this is an interview for the movie.
Alternatively, possible that it’s a bespoke watch. He’s got the money for it.