Ok, im a little confused, are you describing Micro Tig or Micro Plasma Arc Welding? You mentioned orifice diameter, which I was under the impression applied to PAW.
I was poking around weld logics site and I found the Model PA-10/100-STD which seems like it would work, but like all fun industrial equipment on the web, theres nothing saying how much the dang thing costs :( :(
http://www.weldlogic.com/modelpa.phpIm going to go set up my tiny tungsten on my torch and give it a try once I wake up and get some coffee in me, so ill let you know how it works.