Halloween // Costume Advice Needed!!

My boyfriend is going to dress as an old school detective, like a fedora, old school gun holster, suit jacket, all that. Well be riding around in a crown vic to fit the old school style. I need something that'll go with it. It can be from a tv show or just something basic. I've been trying to come up with something but I'm drawing blanks! Thanks! I'll answer any questions asap. <3