I designed airbrush holder that can be laid out side by side for as many units as you need, or put each unit in the box and stack them vertically. The box should stack fine without magnets but there are holes meant for 6mm x 3mm magnets.
The airbrush holder itself is designed primarily for Iwata airbrushes but should work for many other airbrushes. The area for the main body of airbrush can accommodate up to 12.5 mm (about half inch) in diameter.
In addition to single airbrush holder and box, in the raw file list you can find holders for 1, 2, 3, 4 and 5 airbrushes. Only the single airbrush version can fit into the stackable box. There are also versions labelled “short” that can be mounted to the edge of a platform and keep the airbrush with the hose attached.
For properly seating airbrush to the holder, see photo #4. There is a locking mechanism for the air stem.
Please note that airbrushes with bottle inlet will not fit in this holder, but may fit in my other design https://makerworld.com/en/models/31141#profileId-28239. Airbrush with side bottle will likely not fit in either of my designs.