Ive seen t3 phlanges and collectors on ebay (among other places) , add those with a few mandrel bent U's and im sure you could come up with something for pretty cheap, when i figured it out awhile ago it came out to something like 100$ in materials, after that its cut and paste
You can build one basically the same as one of Bob's headers if you go to www.mcmaster.com and search for Schedule 40 pipe. The unthreaded stuff is what you need...a few 90 degree bends and a couple tees. That's what forms the actual header. From there you also need a header flange and a T3 flange. All in all the materials come to about $150. I considering doing it, but realized that if you made one and it wasn't spot on, then things wouldn't fit right after you were done (i.e. downpipe, turbo brace, possibly other things I dunno)