Sorry, can't help with your 'Adventures of ...' story, Lemmax. Have you tried posting on other Korean-orientated boards like Dave's ? Maybe someone who's actually working in Korea will have what you're looking for ? Worth a try methinks.
Meanwhile, I'll offer the following:
Home - podcasts with texts for learners to read and practice. Very basic level (which you say your M4s are). You could extend this by using storyboards (e.g. Chris Fairbanks - Storyboards ) so the learners get to recycle the TL and/or do their own stories.
Randall's ESL Cyber Listening Lab - For ESL/EFL Students Randall's listening lab. Some useful audio files with texts.
Another suggestion is to get yourself down to a bookshop like DK and buy graded readers (with illustrations) and accompanying CD/cassette. To give you an idea, try Around The World In 80 Days. The learners can read along and listen at the same time. The storyline is engaging (important if you're teaching teenage boys) and there's plenty of spin-off activities you can do to extend the theme if you have time and motivation. I also did a graded Sherlock Holmes mystery which was a hoot. My class went on to develop their own mystery and created playscripts which they acted out.
Personally, I'm a huge fan of project work in EFL 'cuz there's so much you can do to keep the learners engaged. The combination of readers and audio seems to be under-rated in many Thai classrooms, mores the pity.