You can buy the hollow pins, which I think you are referring to the one that links the flip lock part to the bracelet. I'm sure I've seen them at cousins UK or another online watch part seller.
failing that, buy a similar sized non branded clasp, and cannibalise what you need?
If its the solid pin with hammered ends, that would be a job for a watchmaker.
Just make sure they are of stainless 316l or similar.