Go to the hardware store. Ask for Roller Chain Links.
There are a lot of places online to buy them. They can cost upwards of $20. That is why I made this instructable. It is not fair to have a Mom or Dad pay $20 for something that cost under $2 to make. I have more design coming.
It is just a bike chain. Nickel plated for rust resistance. you can buy them any where.
I have more coming.