Maybe I can help---what you want is "decorative expanded metal", or just "expanded metal" When people talk about grating, they generally mean bar grating which is used to support people as in overhead walkways and platforms, etcetera. That is why I suggested a structural steel company. If I was going to attempt what you are talking about, I would take a length of 5/16" diameter or 3/8" diameter hot rolled round bar, and form it to the inside size that you want the opening in your hood to be, then butt weld the ends of it together to make a closed shape. Then take a larger peice of the expanded metal, cut a hole in it the size of the inside space surrounded by the round bar, and weld it to the round bar to give the edge a nicely finished look, then let the outside edges of the expanded metal extend back under the inside of the hood hole and weld it on the inside of the hood. To find a source for the "decorative expanded metal" do an internet search.