I wouldn't bother with a damsel to be honest.
How mature is your tank? I would be thinking about maybe a scooter dragonet or maybe a bi-colour blenny or something, or a gramma or dottyback perhaps? If you are feeling adventurous you could try a pipefish like the blue-banded pipefish I have which only gets to about 3" and from my experience is very easy to keep and feed.
Ben