I bought a 15.6" monitor to use with some Linux boxes and as a secondary display on my iMac. There are a lot of these around, sometimes called travel monitors. Mine is this Roadom model (less than $100 at the time). It comes with a case/stand but it isn't stable and I wanted mine to sit nearly vertical. So I hacked this model. The front looks OK but this was my first try and the back side is ugly (fine with me since I can't see it). My monitor is about 12mm thick and the model holds it snuggly.
https://www.amazon.com/gp/product/B09WMXV5SC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
The author marked this model as their own original creation.