I remember "luggable" as the adjective of choice for such machines through the late 80's and early 90's. The PC Magazine columnists (Dvorak and Seymour and others) were fond of it.
I remember "luggable". There was an April fool's section in BYTE in the late 80's advertising a line of hand luggage made to look like portable computers. The text said something about the size being painfully realistic and not fitting under an airplane seat.
Did you notice this Ad they had for Osborne? Please scroll down to see the 'The Guy on the left doesn't stand a chance' Ad, on the 2nd page of the article (http://technologizer.com/2011/04/01/osborne-computer/2/ )
It almost could have been an Ad for a 'Laptop' as we know it.
Erm... "portable" is not the word I'd use. Most would settle for "transportable". I'd rather use "draggable".