Asus ROG Portable monitor: https://www.amazon.com/ASUS-Portable-...
(includes all accessories in video except dock and power bank)
There have been times when the ROG Ally's screen wasn't quite what I needed for a particular game. I use the Asus ROG Strix portable monitor, it's 144hz 1080p VRR display is more than enough to expand my experience and take it even further beyond.

....Let's talk about the BEST portable monitor for Asus's ROG Ally!