I wanted to share a website with everyone.
Red Hill General Store is the best place I've found online if you have a pressure canner. They carry virtually every part you may ever need for most brands of pressure cooker/canner. In my case, I inherited a
Mirro 22 qt. and that link provides all parts for all Mirro pressure canners.
I have no personal interest in the store, but it took me some time to find a store like this and I thought I would share it in case anyone ever needs parts.