I tend to reccomend ReliableHardware for most of the parts, because that gets you grilles cut to your spec, with a greater choice in grilles. I prefer the most open space, a figure which they kindly supply, though I think I spotted a typo'd figure last time I was there.
A tip on cutting, especially the diamond extruded type: don't use a grinder type cutting wheel for a table saw. The extra thickness makes for potential problems. Instead, use a hand grinder with a fresh cutting wheel on it. Clamp the material down with a long straight chunk of 1x4 or similar as a guide, right over and edged to the line you want to cut (you can even forgo tape marking), with that all overhanging your table slightly.
Then you can simply run the cutting wheel's open side right up against the guide board surface to cut straight and true. It may polish up the guide wood but unless you screw the pooch that's all it does. Don't rush or use a lot of pressure and you get really consistent clean cuts.
EDIT: Don't foget eye and hand protection. I often use the blue latex/cotton landscaping gloves because of their tight fit and sure grip for these type of jobs - and when dealing with PL Premium ; }
