In Myeongdong, try Daiso Myeongdong Main (43 Myeongdong-gil) or Myeongdong

Station (134-1 Toegye-ro), both 10am–10pm. The same line's 81 Pure Éclat highlighter is ₩3,000 with 13K+ orders and 1,073 reviews at 4.8. Easy to match with the lip items.