I'm afraid I can't recommend a particular scanner mines an old cheap Agfa one and it doesn't scan negatives, have a look at the PCA charts and see what they recommend. Thing I wanted to mention is I don't know if there is such a thing as a truly portable scanner but worth mentioning I think is that all scanners I have seen come with a lock to lock the scanning head in place when you move it to prevent damage, if you propose to move it about a lot its worth bearing in mind, if you forget to lock it before you move it your scanner may not last long.
Also, of course, most scanners that can scan negs/slides a pretty bulky. About twice the size of a laptop. Also they will probably all work from mains power because of the consumption to do that work. Even if you could find one that worked off USB only would your laptop battery be able to supply enough power to support it? Good luck in your search. Have a look here and see if there is on available: click here