Evil Chris, are you serious?
the "known" suppliers are known by you as well, I hope.
so this is sort of useless, I am afraid.
bulk traffic suppliers must be known by you and heh ........... there are no secret BIG SUPPLIERS I am afraid but then again if you find them please do not hesitate to inform us.
although not bulk maybe
http://www.buygalleryspots.com could help?