When I bought one, Charles & Colvard was a good source. Helzberg Diamonds is also a good place to look, and they can set one you bought online for a reasonable price.

I got a 3 carat moissanite pendant necklace from Helzberg for ~$1500. The same thing in diamond would have been well into 5 digits. My wife loves it and gets a lot of compliments on it.