Post 438068 (https://www.thevespiary.org/talk/index.php?topic=5134.msg43806800#msg43806800)
(moo: "Ammonium Chloride from Ammonium Sulfate", Chemicals & Equipment) but substitute copper sulfate for ammonium sulfate. If you can't get those then you're not looking hard enough. You could also use copper carbonate and HCl.