Just a beginner in this hobby. My son came to me and said I would like something like this.  So I sketched it and created it.  Let me know if you would like stl or other file uploaded.  I am sure there are things out there like this but we wanted to make one that was custom.  You can see he is using it to hold 2 macbooks.  We printed three of these brackets so they are installed on 3 sides for easy slide in and out.