Galvanized nails are only zinc coated steel, where the outside is pure zinc but then it progresses through a mixture of zinc/steel to pure steel.
If you are after wire I am not sure where to get it but for a chunk of zinc go and see a hot dip galvanising factory and ask for a chunk of their drippings. ie the bits that have to be cut off after the process is complete. I am sure if you asked nicely they will be forthcoming. Regards Alan Case