Check out JNJ
They've got some great deals on some SMOKING pastels right now! I got my first pastel from them at a show back a few months ago and they are awesome, customer service is top notch and I know quite a few people that have bought from them with 0 problems and only great things to say.

Also I would definitely check out 8ball as mentioned above. Adam's always got amazing looking animals for sale (don't know about pastels right now but it never hurts to ask lol).

Good luck! Remember, always check the BOI anytime you're thinking of ordering from someone online.

Edit: They've also got a pastel/yellowbelly for sale and some proven breeder YBs as well.