I needed a Sketch Pen but didn't have the time to wait (as need it now).

So made one, find a 14mm OD syringe - this one has the perfect size end to take a Bic pen as you can see - you just have to drill out the slightly more restricted hole between that and the main body of the Syringe.

This works perfectly - no more wasting Meta-Tex just to find out my holes weren't cut out :)