I was looking through some boxes of old minis that I packed away a few years ago, and I found a goblin chief on a warg, which I've identified on google as Golfimbul, the enemy of Bandobras Took.

Is he still a legal model in the game? I can't find a profile in the new Lord of the Rings army book.

He hasn't had a profile for some time now, although even his old profile wasn't much special (orc captain with very slightly modified stats). You can just use him as a normal captain now - it's a nice model.