I bought a set of silver stainless mesh grills for my '04 STI that I never mounted and are still in their original packaging. They were $60 or $70 plus shipping new off ebay, and I think the seller was "The Grill Guy" but I can't remember exactly. They're cut to fit already and include all of the mounting hardware and instructions, and they're both the top and bottom grills.
They're thick high quality strong stainless with round holes. They're not the cheap woven mesh but the high quality stamped pieces where the round holes are actually stamped out of a solid piece of 1/16" stainless. Maybe it's 1/8" but I think it's 1/16", either way they're very strong but still very light!
I forgot I even had these any more until I was cleaning up my garage recently, so I'm selling them at the rock bottom price of $30 including shipping (continental US only). They'll fit any STI or WRX from 2004-2007.