I'm no good to you with recommendations of where to buy, but I totally echo the love for Soca. I picked some up in Tobago, just some dodgy CDrs off the street. Machel Montano is a T&T favourite - I'll up his tune 'Craziness' in a bit. It's just one of the most energetic tunes i've ever heard. I love it.
Interestingly enough, in T&T they have a wee offshoot known as Chutney Soca - it's indian flavoured Soca, there's a big Indian population there whose ancestors were brought in as indentured labourers at the time of slavery.
Another strange thing about Soca - the Carribean (well, T&T at least) is one of the most relaxed places i've ever been, yet they listen to the most energetic music going. Bizarre, but strangely fitting.
Edit:
Soca!!! 'Craziness' and 'Indian Man' by Denise Belfon for your listening pleasure. Oh yeah, there's a 1xtra show too if you want to hear more and are out of reach of london Soca pirates.