[Dave Paine]

I don't have jaws to hold a pen blank on the lathe.

I'm sort of thinking about drilling it using a 1/2" Forstner bit and enlarging it using my drum sander.

I presume by drum sander you mean spindle sander. You will not find it easy to get an even round hole with the spindle sander.

If you cannot drill on the lathe, I would use a drill press with the correct size bit. Just need to clamp between two scraps of wood with a "V" cut out in each.