I searched for quite a while until I just changed the whole indicator. The new Touring version has clear lenses, but no one has posted as to whether they will interchange or not.
That's unusual for Triumph to make things for only one bike. Ever since they started making bikes again they prided themselves in the cost savings of using parts for several different bikes. I just bought clear lenses from a Daytona 675 that fit my wife's Daytona 600. Too bad they don't fit the Rocket...