In Myeongdong, the Namdaemun-ro side has Olive Young Myeongdong Timewalk

(Timewalk Myeongdong #108–109, 78 Namdaemun-ro) and Myeongdong 2-ga (68-1 Namdaemun-ro). NODOR solid mouthwash is, as the name says, solid rather than liquid, so it's easier to pack.