Zinc

Caswell and Eastwood each offer kits.

DIY

This page provides a simple rundown of how to do some zinc plating. The basic "recipe" is:

Fill the container about half way with vinegar (vinegar is mild acetic acid).
Put the zinc anode into vinegar and let it sit for several hours, allowing some of the zinc to dissolve.
Add 100 g/l of Epsom Salts to increase conductivity
Add 120 g/l of table sugar as a "brightener"
Connect one flashlight battery (1-1/2 volts) to the penny and the zinc anode
Place anode and penny into the solution. Don't let them touch each other.

Penny should be coated within a few minutes.

Where to buy zinc?

Go2Marine.com has 3"x3"x0.5" plates for $8.95, and 3"x6"x0.5" plates for $10.82.