Update: You can check new version with more slots:

Brush holder 6 slots od autora Many24 | Stáhnou STL model zdarma | Printables.com
I was looking for very simple holder for just a few brushes, but none of them fit my needs, so I made my own version.
It's very simple and minimalist design, and also quick print - roughly 30min.
The author marked this model as their own original creation.