I'll post a photo tomorrow (night time here!) when I have time to take it apart, but I'm *pretty* sure that we're talking about different parts here. This is not a part of the stem, it's just a little piece of metal that goes around the stem and holds it in place so it doesn't pop out of the case. It's literally in the case, not in the movement.
I'm new to watches, but this is a system for holding the stem in place that I haven't seen on any of the few modern watches I've poked around inside.
I've looked on ebay, but unless I'm searching with the wrong term, all I can find are junk