I have a few lying around someplace, but I also have a couple of MK5s that might need them. Honestly I would not worry about it too much. Have a good close look at the brass bolt with a jeweler's loupe; you should be able to see any obvious signs of damage. If it looks good, just use it and don't overtorque it. I've only seen one or two that had any signs of damage.
I said "might" need them because it's a low enough priority for me that I'm not going to specifically take one apart just to change the bolt. Whenever I rebuild one (not that often, those things are good for a lot of dives between rebuilds) I check the bolt. I can't remember the last time I switched one.
The earlier MK5s used a circlip, as has been noted. Take a look at those puny circlips and you'll get an idea of how little the stress is on that connection.
I bet Bryan can put his hands on one for you; if he's out, it wouldn't surprise me if he does another run.
