Am I missing something at Berea Hardwoods? I don't see these parts or even a kit that is close to the same style. Can you post a link to it?
Berea doesn't sell individual parts for the most part, and they do not sell the Baron as they have agreements to vendors for that specific kit. Arizona Sil. in the States and Woodwrite in Canada. The Navigator is only sold through Woodcraft to the best of my knowledge. And to my knowledge none of them sell individual parts.
Now, only the rollerball Baron has the hex nib holder, the fountain's is round.
The Tycoon is a PSI kits, and may be available through some of the resellers. I don't know if you can get the parts individually on them as I haven't bought from any PSI people in a long while.