What music libraries your are using? Can you advise some not very pricy ones with rock, ska, raggae, so modern music in good quality?
Search MySpace, Facebook, and other places bands put music and contact them about using their music in whatever project you're working on. You can possibly get music for cheap or free that way.
Another option is to look for composers that can easily write that stuff for you (for instance, I've played in rock, punk, metal, ska, and reggae bands for the last thirteen years).