Daniels/Kovich encountered an American missionary in China in the late 1920s who was a skilled plastic surgeon in civilian life and while the surgeon specialized in earlobe reconstruction, he also had experience with hair reconstruction.The only issue with this reveal is that ENT Daniels was VERY VERY CLEARLY bald and wearing a toupee, when Kovich has a full glorious head of silver hair.
Before you suggest it, hair plugs were banned during the Eugenics Wars.