At the Computer History Museum in 2015 when they hosted the 30th Anniversary event for the Commodore Amiga (https://amiga30.com/) I saw a prototype luggable Amiga in basically the same form factor. I'm forgetting the model number designation on the label (and the picture I took is presumably on some hard drive offline in storage) but I guess they made 3 of them? Never something that went to mass market.

It looked like this more or less:

There is more information on other "portable" Amiga efforts (they almost all seem to be bespoke/custom, whereas I got the impression what I saw at the Amiga Anniversary event may have originated officially within Commodore?) here:

http://www.bambi-amiga.co.uk/amigahistory/portamiga.html

I think my first thought about portable computing in my youth was when I saw a Seiko TV Watch at some store and wondered if I could hook up the output of an Atari 2600 to play video games on it?

OFC, Alan Kay had similar insights, in the late 1960s and that is when he began working on his idea for the "Dynabook" also see: https://en.wikipedia.org/wiki/Dynabook (what we now would call a "tablet" computer like an iPad or whatever).