Recommendation on a portable extra screen for my MacBook Pro

I am about to buy a MacBook Pro 16' and I will be travelling a lot next year. I am a graphic designer and need a larger screen, and I am hoping I can find a good plug in monitor that is light and slim enough to be portable and offer the extra screen space I need. I have checked the internet and am completely confused by the choice. I have spoken to Apple and appalled at the lack of help they offer. I have asked various tech support lines and in-company tech departments. Can anyone help? I can't believe I am the only Apple user on the whole planet who needs this - there must be a clear answer to this. Help please!

[Re-Titled by Moderator]