You can buy eyelets (also known as grommets) at most sewing retailers in a
variety of sizes and metals, as well as colors.
Most of the time the retailer also offers the tool needed to set the eyelets as well, it's fairly inexpensive.
You do need a hammer along with the tool.
Vintage Threads' step-by-step photo tutorial is sure to inspire you! Get the tute!
You can buy good quality eyelets here.