I have only come across Korean subtitles for kdramas in Korea so far. You used to be able to find transcripts for SBS dramas over their website, but that function seems to have disappeared. In any case, the transcripts were quite difficult to follow, as the dialogue from the entire cast was all mashed together. Took me ages to match the transcript to the drama and I gave up after 2 episodes. Have you tried drama comics? You can find manga versions of popular dramas over gmarket. Search for 드라마 영상만화. Hope this helps!