Where do people get their new genuine Rolex parts? Will AD help?

[DaveInLA]

My understanding is that Rolex aggressively controls their parts distribution to restrict the counterfeit market. However, I've seen many people sell new bracelets, links, clasps and bezels, and I'm left wondering where they got these parts. I've heard that if you take your watch to RSC and they replace a part, they'll keep the used original piece so that nobody has spare parts. How do some people get these parts?

Specifically, I'm trying to get a new clasp; I'd like to get a SD 93160 clasp for my Sub-date, but RSC won't help me with this. Does anybody know if an AD will be able to get a new clasp for me? Thanks