This Daiso ceramic doodad (12 for $20.16) was not originally designed to hold ink sample vials but it’s absolutely perfect for it. It’s actually designed to hold a toothbrush.
Sample vials (5ml size) fit in this ceramic holder perfectly. It keeps me from tipping over a sample vial when I’m doing swatch samples or just playing around with the ink.
I left the sticker on the bottom so that I could share it with you and provide information as to what to ask for in the store. There are also elephant shaped holders and pig shaped holders (8 pieces for $13.44). There’s even a white ceramic model with a triangular base (16 for $26.88).
If you don’t have a Daiso near you, you could make something similar from air-dry clay or polymer clay. I think I might dig around in my art supplies and see if I have anything I could use to make a couple of my own.