I've seen plenty of my students wearing them so I would guess they are widely available. Have you tried shoe shops such as ABC Mart, Les Mores and the Athletes Foot? They are everywhere, but are all together in Nampo near KFC and Seomyeon on the street that runs behind Judie's Taehwa.
they dont have them at those place listed above. you would think they would carry them...but they dont! i just ordered a pair from shinsegae's online mall. they were around 55,000 won. shipping was a nominal charge and they got to me super fast- less than 2 days! happy shopping :)
If you are not seeing them in the normal shoe stores (ABC-mart, etc.) they may be a seasonal item. They should be back on the shelves in spring.