[Jmirko]

If size is the only problem, I think a home-made solution is fine. This is my take on this (see attached photos).
The key is to use a pen which can be unscrewed in the middle. Cut off the tip just enough so the stylus can't slip out that way. Insert the spring on top of the stylus so it holds it nicely in place.
It's indeed much easier to write with. Storage is not as elegant as the factory solution, but it will keep you from losing the pen.