For mounting I use either CA, 5 minute epoxy, or Gator Glue.
I don't use copper foil, but sometimes use brass foil, better known as brass shim stock.
K&S Engineering use to sell a small package of various thickness shim stock, although I no longer see it listed My lead foil I picked up years ago from a long forgotten place I ran across on the internet, it ran me $30.00 for a 5 pound roll of .006 thickness by 3 inches wide lead foil. It has turned into a life time supply for me, sorry I no longer have the link, nor remember the name of the place since it was on my original computer, and when that died so did all the bookmarks.
Most on line hobby shops carry some sort of lead foil, under various brand name, Verlinden is one that come to my senile mind.
Brass and other metal shim stock, you can find at just about any engineering outfit.
McMaster-Carr carries various thickness of shim stock. Do a search for Shim Stock