Tried printing the pen laying down. Print didn't turn out very clean. It also needed supports. My printer isn't as great as Jeremy's so tried printing vertically with a sturdy raft and some brims to make the base wider so that the pen would stick to the surface of the print base.Added a cone inside for support.
Update: Previous version needed significant scaling. This version I've scaled it up already. Also cut it in half because of two things...
1) easier to print - no risky tower that could disconnect from base
2) just incase you need to do some adjusting to the inner diameter of the shaft. You may need to bore it out to make your bic pen fit.
Depending on what type of pen you are putting inside. In this case a bic pen. you may need to bore out the inner diameter.
Some light sanding and removal of some ruff sides or pieces of plastic sticking out. if any.
picture to follow