Well, Master Choe knows where most of the Tang Soo Do/Soo Bahk Do, Hapkido, and Tae Kwon Do Do Jangs are near Osan, he doesn't know of any other styles. I am taking a trip up to Osan this weekend and I'm hoping to see my Kwan Jang Nim. While I'm there, I'll ask him if he might know of any other styles near there. My headquarters school is in Itaewon, if all else fails, I will ask there when I take a trip.
Sorry I couldn't be of more help!