Cheongsachorong (청사초롱) are traditional lanterns, originally used for weddings in Korea.
They are made of red and blue silk.
Cheongsachorong By Minseong Kim (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons
Where can I buy an authentic version of these - ideally in Seoul, or elsewhere in Korea?
While I couldn't locate any permanent shops online, there's one event where you can certainly get a lantern: Seoul Lantern Festival. It's an annual festival held every November in Seoul. The official website lists prices for many different kinds of lanterns:
Rectangular lanterns: KRW 15,000 / Hanji lantern (3 types): KRW 10,000 / Color lanterns: KRW 5,000
I therefore presume that there is official lantern store on the grounds where you can get a cheongsachorong.
