If anything else drill out the cork to make a floating sleeve/cover for the ferro rod.
Ohhh man.. I got a killer idea for a spark stick now to include a cork.
I once did a project from an article about tinder boxes. Mine was more of a tube, As shown below:




Now make that a bit less deep, put PJB or some other tinder in the tube, and fit a ferro rod to the other end. Add a few pieces of fat wood to the lanyard, and you got a snazzy fit kit.
..just saying.