I order it by the case from my co-op,
Azure Standard. They carry Natural Value (not organic, just coconut milk and water), Native Forest (organic, coconut milk and water and guar gum), and Thai Kitchen (organic, coconut milk and xanthan gum and soy lecithin). I usually get the Native Forest, though it is the most expensive (at $16.30 per case), because I want organic, but I don't want soy lecithin. I am still not sure what to think about guar gum -- I've read a lot of conflicting reports -- but I do know that very, very, very little is needed to work as a thickening agent, so I'm ignoring it at present.