Just search youtube for "lost soundtrack" - someone's added the first three seasons' soundtracks on there and they have a website you can download them from (link in his profile). I love Michael Giacchino - one of my favourite composers. I'm thinking about becoming a TV soundtrack composer and he's a massive influene on me (although he overdoes the chord I-III movements). He uses leitmotifs almsot as well as Wagner did.

Still, maybe you should consider buying the soundtracks?