The one starx is using in his 'movie accurate ironman' build thread looks amazing. It is from dungbeetle I believe, but I don't know what he charges for his pep files. But to be honest, it looks completely worth picking up.
Im gonna agree with coolguy26 and Lord Farquaad here. Dungbeetles helmet file is amazing. I was originally going to go with sharkheads file, but i put the work into dungbeetles and it came out perfectly. Its around twenty pages, and a little taxing if you can't get the sizing right, but its definitely worth it. Heres a picture of it for your reference (not intended to thread jack or anything)
I think dungbeetle only charged five dollars for it. Its a sacrifice i made for accuracy. But if its just for a display, i dont see why you wouldnt want to spend five bucks. Cant wait to see your progress on your helmet though! Keep us posted.