Turn you regular drill press vice into a self centering pen vice.
You can either tape it to your vice or use 10x3mm or 10x5mm magnets.

Doesn't Matter

.2

100

Print it as oriented for strength. To make the magnets fit better, use support inside the holes. I used 3 shells at 50% and I can hear it creaking when I use it. I would recommend close to 100% fill.