I saw a thumbnail from YouTuber Matthias Wandel where a stand just like this was visible. As I was in need of something similar I decided to throw together one in Onshape before checking his video.

From early testing it seems to work fine. The base is hollow to allow for some weight to be inserted so it'll be more stable. The friction between the top and the bottom is low so it makes it easy to adjust, but I am considering adding something grippier so it's not as slippery.

The base is hollow so it can be filled with something heavy.

A template for cutting a foam (or similar) layer to place on the base is included as a PDF.

The CAD file is available here: https://cad.onshape.com/documents/2e206f08a7a577552792a514/w/d98def250a09cad23ac082f4/e/0cacf6f66fa8e0a933eacb2f

(Don't judge me! I am not used to CAD and I threw this together quickly)

Check out Matthias Wandel here: https://www.youtube.com/user/Matthiaswandel