Myeongdong stores: Olive Young Myeongdong Town (53 Myeongdong-gil, 1F-2F) and

Central Myeongdong Town (M Plaza, 27 Myeongdong 8-gil, B1-3F), open till 10:30 pm. Nipple covers aren't liquids, so carry-on is fine. The covers with 프리플 in the name (8cm/10cm) have 1.5K+ reviews. The two are close, so if one is out of stock, try the other.