I've been living in Seoul for 7 years now and finally discovered SHOES!
In an area called Edea, not too far from where I live, is the best place to buy shoes. And if they don't have your size (most of the shoes here are smaller sizes) or style, don't worry, you can get whatever you'd like made.
Another great thing in that all the stores are in the same area, shop after shop. So if one store doesn't have what you want, just head next door.
I think it's funny how they are all lined up in rows, but it does make sense. If you need shoes, you just have to go to this one street. Actually, many of the vendors are this way like mirrors and pets. Need toys? Head over to Toy Alley (a tiny street of toy vendors).
So if you're ever stopping through Seoul, come grab a coffee and we'll go shoe shopping. There are lots of great deals to be had!