There are plenty of celebrities who have undergone hair transplants. Most do not tell about their operations and they are often silent how they keep up a young appearance. But there is a brave bunch of celebrities who are open about their transplants. I have promised to be silent about some very famous people that are excluded from this list.
Actors who (probably) done hair transplant.
Politicians who (probably) undergone (not so good) hair transplants
Sports Profiles that probably have undergone hair transplants