Looking for a bracelet pin

Could anyone advise the pin needed for a 1504/826 bracelet (on an Omega Seamaster Chronograph)? A friend has one that popped out and, like a fool, I said I'd get him one and pop it in. Of course, nothing I have in my box o' bits is a good fit so I might as well get the real thing if I can. Thing is, I'm just confusing myself with Ofrei and Cousins - is this part not available in the UK from third party retailers?

Thank you, Al.

It's been said before but it bears repeating - you're a godsend when it comes to finding part numbers (as well as sharing your experience and knowledge in all other aspects). That part number shows straight up on Cousins and they have them in stock. There are no tubes in the links, so that may well be the part that failed and then the pin fell out. I've had the bracelet off and run it through the ultrasonic cleaner but I think I'll run a cape cod cloth over the clasp for him too (he wears this every day in alsorts of conditions and it shows!).

There's a couple of photos below if you wouldn't mind looking and please tell me if I'm doing anything wrong with ordering the regular pin and tubes.

Thanks again!