Forgive my ignorace, but what's wrong with ye olde fashioned welding helmet?
I got one for $10AU and it's great. I even used the crummy plastic lens for a while but it was a bit light so I replaced it with a glass lens and spatterguard (about another $10AU) which was even better.
Then again, I may be a retro grouch/tightarse since I also use an arc (stick if you prefer) welder
Nice to see your build is coming along well anyway.
**edit**
On closer inspection that first photo was of a crappy helmet without a flip up lens.