I've been to a bunch of metal places and they just have heavy
wide-gauge stuff the likes of which you'd use to keep raccoons out of
your basement or something.

After Googling "hex mesh" and "perforated sheet metal" instead of
anything with the term "grill" in it, I did come up with this place,
which looks to have several viable options:
http://www.mcnichols.com/products/perforated/

I've seen some bulk grille material sold by one of the "ricer" companies
- APC? - and it actually looked pretty good.  Kind of like what used to
be called "stretch metal" but smaller and lighter.  Thought about buying
some to make a stone shield for the radiator on my '55 Stude, but the
pieces sold were too small to be used for that app.  I think I actually
saw this stuff on close out at "Ollie's" - a chain similar to Big Lots,
so it wasn't expensive at all.

On the opposite end of the spectrum, I was leafing through some back
issues of Excellence while waiting for an oil change/safety inspection
on my company car this AM; there was an article on some new gravel
shields custom made for the openings behind the front wheels of the
Carerra GT.  They were laser cut from a CAD program and the little
hexagonal openings in the sheetmetal perfectly matched the pattern of
some other grille on the car.  I don't remember the price of those parts
but I imagine I couldn't afford to have something like that done :(

nate

(can't afford a Carrera GT either, sadly.)