last year, in a search for affordable baking supplies, i came across a place in banyeo-dong.
it's a warehouse/wholesale place that sells most of what you'd need/want to bake =)
it's just behind the banyeo-dong bus terminal at the edge of busan (kind of a pain in the butt to get to, but worth it i think).
it's called "woongjin foods and bakery", 011-564-3453, 051-758-5231
website: www.wjfnb.com (english section still under construction)
on my most recent trip, i bought:
parchment paper
high-quality cocoa powder
big bags of coconut
vanilla extract (only sold in a pretty big bottle)
oatmeal
big bags of icing sugar/confectioners sugar
chopped walnuts
lots of other stuff available and the staff are very helpful and don't mind explaining stuff to you.
they used to have a location in gwangan but it has been closed for over a year.
check it out if you have the time. i love to bake and this place has made it easier for me to do so in busan.
http://www.ilovecookie.co.kr also has a good selection of baking supplies.
happy baking!