Suggestions for touring main Rome historic sights with limited mobility

My husband walks with a cane/walking sticks and we want to tour the main historic sights in Rome.
Vatican, St. Peters Basilica, Sistine Chapel, Colosseum, and Le Domus Romane di Palazzo Valentini. Looking for tour that is reasonable in price that provides wheelchair or any suggestions with best way to navigate these sights is appreciated. Thank you.