The Vapor King is a KR808d-1 that is specially branded for Vapor4Life. It's compatible with all KR808d-1 components from other suppliers. The cartomizers are exactly the same design (wick/batting + mouthpiece + everything else), though V4L has custom labels on their pre-filled cartomizers.
So, buy some empty ones from anywhere you want -- if they're KR808d-1, you can fill them up with your own juice, and put them on your Vapor King battery. (Filling tricks vary; you can find videos on Youtube or plenty of posts here on filling/refilling cartomizers.)