This holder was modeled after the Faber-Castell S markers, although the other tip sized markers should fit too, as well as any marker that's less than 12 mm in diameter, these are just the only ones I had on hand. It can be mounted anywhere with double-sided tape and has an indent in the back so it sits close to the surface it's mounted to.
It was intended to hold 4 colors of markers, but idk where I misplaced my green one, so another black one will do.
The author marked this model as their own original creation.