For travel I always brought one of these as us zenscreen https://www.amazon.com/ASUS-ZenScreen-MB16AC-Portable-Monito... they are powered off the USB.
cat ~/bin/brightness
#!/bin/bash
#
echo "increasing brightness/contrast of external monitor"
/usr/local/bin/ddcutil --display 1 setvcp 10 40
/usr/local/bin/ddcutil --display 1 setvcp 12 10
Tie the above in with your init/resume scripts and you're good to go (assumes that your issue isn't limited by the hardware itself).