Roof flashing gets thinner than that, but it's zinc galvanized which sucks for solderability. Also is probably in roll form, which sucks for flatness (does the laser cutter have a vacuum bed or anything?).
Hardware stores at least around here, only seem to have the tiny decorative pieces, super expensive for what they are. That, but industrial sized, would be great. You'll have to look around real suppliers, maybe order a few kilos worth (hopefully less than a tonne?).
Tim