I picked up Lenovo's ThinkVision M14 about nine months ago now and have been absolutely in love with it. My biggest draws were the IPS display, USB-C, and the reviews painted it as a pretty sturdy device (I travel with mine, so it was a huge concern)

Like OP, this is my first portable display so I have nothing to compare it to, but thought I'd chime in with my praise of Lenovo's monitor. (Note: I picked it up straight from Lenovo with a coupon and I'm in graduate school so I got an extra 10% off, iirc... I paid around $168) - I've had zero problems with it on Windows, Mac, and my Pixelbook.

https://www.amazon.com/dp/B07YX5NKK2/ref=cm_sw_r_cp_apa_i_WQADFb7D6AKV7

Since nobody else has, I'll recommend a portable monitor I really like, the Lenovo ThinkVision M14. I have a ThinkPad (a T480) and it uses the exact same physical screen that's installed inside my laptop, so it's a perfect match. It's really lightweight and gets all its power from the same USB-C port that provides the video signal so all you need to use it is the monitor and one cable. My only gripe is that it will only work with laptops that support DisplayPort over USB-C, but that encompasses most recent laptops. If you know what laptop your son has, I could definitely make a more specific recommendation. Merry Christmas!