I have used this one for several years now and it has worked very well for me:
https://www.amazon.com/Centering-St...argid=aud-801381245258:pla-715100148872&psc=1
I bought mine from Woodriver, but this is the exact same unit and less expensive.
I made up a fixture to set securely and tightly on top of my drill press table. It has a frame on the bottom side that fits snugly around the sides of the drill press table so I can take it on and off in literally a second, yet it keeps it on center when in place. To set it up, I marked a very square blank with a centering tool, placed it in the vise, and then using a brad point bit in the drill press and moved the centering vise to where the my center mark on the blank lined up with the tip of the brad point bit. I then marked for my mounting holes and secured the vice to the fixture with some screws. The mounting holes / slots of the vice are large, so you can use a bit smaller screw and leave yourself with some "play" to fine tune your alignment to the center. Fortunately, I don't drill much else on my drill press, so I'm not moving the table up and down often which will of course throw off your alignment. However, I keep a scrap blank marked for center so I can easily re-align and it's pretty quick and easy once you have it set up once. I probably spent 45 min to an hour in making this fixture, but it is so worth it in the long run if you make a lot of pens.