Offhand, I don't. I know there are some in both places, but I haven't been to them in years. I usually pick up gear when I'm back in the USA, or head to Jongro-5-ga in Seoul. When you get off the subway, you can't miss the gear shops. Every brand. Work your way into the alleys behind the street-facing store fronts for even more selection. This is generally the best selection and prices in Korea.
"If you can't do something well, you might as well learn to enjoy doing it poorly."
-- from a de-motivational poster, but I find it oddly liberating