have your wizard wear loose chains that don't restrict his somantic part of casting and a bag over his head that he can see through, thus making the wizard appear like a prisoner and not a worthy thing to attack, continuously mumble and wave arms around like a crazy prisoner to disguise your spell casting. i feel this would be a cool strategy, now you don't need to worry about armor. or if you are smal like a gnome get carried around in a crate or some sort of bag that gets put down when combat starts, have peep holes so you can see in all directions, now you have cover to grant disadvantage on people attacking you and are hidden. i am assuming that the wizard isn't casting spells that fly from him though rather controler type spells like wall of force and stuff that makes combat nicer for team mates. clever ways to avoid being a target of attacks wil make mage armor unnecessary.