In 1997 Johnny Depp was Donnie Brasco. The movie was about the true story of an undercover cop actually living too close to the mob in 70's New York. His real name is Joseph D. Pistone, an agent of the FBI. He followed the undercover work with the book "Donnie Brasco: My Undercover Life in the Mafia", 1988.
This is your next great idea for a Halloween costume. Wear it for going out or for the big Halloween party that you are planning.
The real point here is to highlight Depp's costuming in the movie scene on the party boat. He wore the classic teardrop aviator sunglasses like Ray-Bans. Now the glasses come in every color imaginable and with the important UV protection. The scene is a mob boat party and his friend Lefty is out to impress the Mafia syndicate.
Finding the light-hued leisure suit would involve a few trips to second-hand stores. Note that it is not white. Look for tan or taupe in order not to be mistaken for the disco dancing guy. Do not wait too long or you may come up short on completing the whole look. You have to keep an eye open for the white long collar dress shirt, 70's style.