Modeled this in Fusion 360.
It was designed for my Intuos pen, but it can accommodate various pens.
The upper hole is 14mm in diameter and the bottom one that the pen rests on is 6mm in diameter.
The initial design had a cut in the middle of the bottom part, but I uploaded it here with the full surface as someone might want to secure it to the table with a double adhesive tape
This was printed on a Form 2, but I would assume any FDM would do the the job.
The print was mildly sanded. I need to go with finer granulation.