Just about no one under 35 has ever seen a copper nail. The old hardware stores used to carry them, and we used to buy 100lb wood kegs.
Go to a hardware store that specializes in roofing.
It is getting harder to find.
BTW... you know how to make an electric pickle?
Strip a lamp cord , wrap one bit around a copper nail. the other bit in a galvanized nail.
Shove one into each end and plug it in...
https://www.youtube.com/watch?v=aab8VjzuXyM