Following the last post I was asked by a couple of followers about the system I use to hold my brushes. My system is Art Box and Panels. You can purchase a brush holder with the system - a simple PVC tube that works well. For me, it was too small. So I purchased larger PVC piping, put caps on top and bottom pieces and a joiner piece to make the holder and attached with a bit of Gorilla Glue .
I drilled holes for air drying of brushes. At the appropriate height I made a double hold that will slide over a screw attached to the back corner of the palette.
The base with the brushes attaches to one side. The top holds my maul stick, straight edge, palette knives and rubber shapers and attaches to the other side. Very happy. Cheap and simple.
The other one I like is the hanging brush holder available from Guerilla Painter.
This shows it hanging from my Soltek easel.
And finally, I had two Artwork Essentials systems that I also liked and they have a really good brush holder .
Hope this helps.