Okay, yeah I forgot about Rand in CX. I'm not sure I'd count Kirk in WALGMO as it's essentially the uniform of those guys on Exo III not really civilian duds.
And I really don't count Kirk and Spock in 20th C clothing in CotEoF and A:E as those were both sort of "undercover" and dressed in local costume for the mission, not in their own clothes on the ship. If we were to include those occasions then that opens it up a lot and we should also count Kirk and crew in "Return of the Archons", Kirk and Spock undercover on Organia in "Errand of Mercy," Kirk and Spock dressed to the nines in "A Piece of the Action," Kirk and McCoy undercover on Neural in "A Private Little War," Kirk, Spock and McCoy dressed as Nazis in "Patterns of Force," the guys in neo-Roman slave T-shirts on "Bread and Circuses," Kirk in Romulan gear in "The Enterprise Incident," Kirk as Kirok in "The Paradise Syndrome," and Kirk and Crew in those Greek get-ups in "Plato's Stepchildren." None of which is an example of what they might wear in their off-time on board the ship.
As for ATWIHAIHTTS, I don't think McCoy ever did change his costume.