I just purchased a couple "new" Swivomatic collets from Al Drew's Music Center. Yes, these are aftermarket parts, but they are excellent! If you're not concerned about authenticity, but want a forged/machined collet that is designed better than the originals, please check these out.
They also sell under the ebay name of "aldrewmusic".
Here are some pictures of the three types I have.
In this order: Original Rogers Forged/Original Rogers Cast/Al Drew Forged
-Tim