Dude i could weld up a manifold here at my house for a 2j, its not like that piticular motor needs special skills and tools over any other motor.

Local shops that i can think of off hand in the tampa area that know how to make manifolds and are willing to make one
secret services offer manifolds all the time,
Rameies automotive do all kinds of fabrication including turbo manifolds, headers ect. mainly for mustangs.
Street heat would have no problems making one im sure.
theres another shop i cant think of the name that i know they did a Is300 turbo, really not sure if it was just a kit tho.

slightly outside of tampa...

titon, garage advance, high tech. to list a few off the top of my head.

and of your list you forgot the Inventor of the NA-T Jerret humprys the owner of power house racing. who sells an NA-T kit. also sells some of the most bad ass turbo kits for the TT supra. mostly made to order but hey thats how i like it. one of a kind.

but really its only a fucking manifold. any hill billy with a mig can zap one togather in a few hours. and most of these hill billys come with many years expernace in racing manifolds and paking nice Tig welders.