Yep - you buy them.
Making a nib is not an easy or cheap process.
The tipping is where all the trouble comes in. You've got to be able to arc weld (or some kinda weld) this little ball of ruthenium to the tip of your gold nib. Once you do that cut the slit.
There's actually a lot written about it, and how hard it is, over at Fountain Pen Network.
Use this google searcher and look up terms like
Google Custom Search - The Fountain Pen Network Search
retipping nibs
making nibs
home made nibs
Somebody made some titanium nibs last year but w/o tipping.