Myeongdong has Daiso Myeongdong Main Store (43 Myeongdong-gil) and Myeongdong Station Store (134-1 Toegye-ro), both open until 10 pm. If you can't find them, show staff a product photo. Silicone straps (4) are ₩1,000 with 4K+ orders, and bear-shaped holders (4) ₩1,000 with 3.8K+, cute gifts for coworkers. All small, so carry-on is fine.
Daiso Mall
Daiso MallDaiso Mall