Just about any trusted vendor here on PS can source melee for you upon request... Most of us probably don''t post prices for melee on the web site, but drop an email with the carat weight, number required, desired clarity and color and any dealer can take care of it for you.
You may actually save money by buying the stones from whoever you are planning to have set them. Pretty much any jeweler can get them. The problem is that the setting charges may be different depending on whether or not they supplied the stones.
Have you chosen a setter and have you spoken to them about the project?