This is by no means a complete list, but it is a list of some suppliers of steel that I have used or that have been used by friends of mine in the past.
Kelly Cupples
2807 Butterfield Rd. Yakima, WA 98901 509-949-5231 octihunter@charter.net http://elliscustomknifeworks.hightemptools.com/steel.html Kelly is a fantastic guy to deal with. He's one of my favorite "steel pushers".
Aldo Bruno (The New Jersey Steel Baron)
aldo@njsteelbaron.com Aldo is famous for his occasional mill runs of 1084. He also has 1095, O1, 52100, and a host of other things that he finds. Another great guy to deal with. Email him and see if he has what you need.