Big Bang, 'Ssonda'
I loved this film, it's a shame so few people have ever even seen it.
If I were to describe it, it would be something like a Korean version of "Nothing to Lose" (Tim Robbins, Martin Lawrence) with a generally darker tone of humour and a lot more drama.
This won't tell you exactly where to find it (since it's listed as out of stock) but it'll give you an idea of what to look for. :)
http://www.seoulselection.com/shopping_dvd_view.html?pid=1339
Have fun,