I think you can even buy them at the airport from the Royal Caribbean desk by the luggage carousels. If I want them I let my agent know and she takes care of it.
It is important about the departure flight time when using the shuttle buses. A bus won't leave the port until full and you can cool your heels for a while just sitting there waiting for people to board. I once left the ship at 7am in Port Canaveral and was thinking I could make a 9am flight that still had space. I was willing to pay the rebooking fee since my booked flight was not until 4pm. Nope. I sat on the bus for an hour until it was full. Got to MCO in time to see my hoped-for flight leaving and I got to sit in the Sky Club for 6 hours.