www.jgstools.com They have complete ready to use manifolds or you can buy a manifold kit if you need something custom.
Tom also has beautiful quality manifolds but I am not sure if he would part with one by itself. You might ask him though. I don't know of your ability but you could make your own. I mad my own. Bought a .500 head flange a .500 turbo flange then went to the plumbing and bought 2 "T" and 2 90 elbos schedule 40 .125 pipe. Tig welded it all togeather. Came out great.