In Seongsu, Daiso Seongsu 2-ga (106 Seongdeokjeong-gil) and Ttukseom Station

Store (6 Achasan-ro) are open until 10 pm, fine after cafe hopping. 걸이식 전구 모양 LED 무드등 is a hanging bulb light for ₩3,000 with 2.7K+ orders, pretty by a window or bed. Lights can break, so wrap them in clothes in your suitcase.