I see that markablue liked the option behind door # 3 ... even though,

forgot my tinfoil hat today

Actually, I prefer the aluminized mylar shower caps ... they are far less likely to tear than the usual hand-made tinfoil caps. 

At the drug store (chemists), if I saw magnetic copper bracelets, I would inquire about the aluminized mylar shower caps -- all of those items should be together ... since they all work on the same principles. 

--
Martin