To clarify what I'm doing, I know I could buy them, or laser drilled brass, etc., but my intention is to fabricate every part of this camera that I can reasonably make by myself. The camera will be an 8x10.
To me the beauty of a pinhole is an all hand made camera with a hand made pin hole and the joy to be had in doing it. I don’t get the high tech laser drilled pinhole thing at all. To me it just misses the point.
I second greybeard's suggestion. I've made several that way, the first out of an aluminum soda can sidewall (!) that is about 0.004 inches thick, the later ones out of 0.002" brass shim stock. Many -- well anyway, "good" -- hobby shops stock assortments of metal stock -- rods, tubes, strips -- and among the choices is a pack of brass shim stock in sheets about 4x6 inches in thicknesses of 1, 2, 3 and 6 mils or somewhere in there. 1 mil is pretty flimsy to handle, although with patience and good manual dexterity it's possible. 2 mil was easier. I used 400 wet-or-dry sandpaper to sand the bump down using a gentle circular motion. I would think stainless this thin could be worked easily enough too.
I agree with DWThomas: .002" brass shim stock is easier to work with than .001". Rather than use fine sandpaper or emery paper, a very smooth and hard whetstone also works well. When making very small pinholes, I pierce the dimple with an ordinary sewing pin held in a pin vise, and keep the pin in the hole while grinding down the dimple. This slows the process down slightly for more control, and gives a fairly clean hole.
Shim stock, feeler gauge stock, emsdiasum.com for electrodeposited copper single hole 3(.15) mm diameter electron microscopy grids, around $25/100. 600 and 800 micron are standard and you couldshare them, sell them or teach a class with them.
I've used .001 stainless shim stock both for pin made pinholes and laser made pinholes (I have access to a not-quite-powerful-enough laser cutter). It works really well, but it is a little difficult to handle being so thin.
my preferred pinhole material is from aluminum cans... preferably guiness as they're already black on one side ( ) but in a pinch any of the canned beverages will suffice. That said, I taught an elementary pinhole workshop recently and because I was in a hurry to get all the materials together we used pie tin material and it worked great.... i was surprised. good luck, keep us posted!