Any 3mm neoprene hood that covers neck and outline of face will do, O'Neill for example.
Just make sure it sits outside the drysuit neck seal to prevent water from entering.http://www.oneill.com/#/men/europe/coll ... d_1/black/
I don't know the ion suit, but you can always cut off excess neoprene at the neck if the drysuit hood gets in the way.
A thin 1mm hood can work earlier in the season and is much more convenient.
Other than that it is fit and personal preference - how much of the face to cover etc.