I don't believe you can buy them in the aftermarket. These are a pair I've had kicking around for years. They're in really good shape, just a little dirty and some paint on the edge.
These are from a 68 Parisienne, so I'm not sure if they're the same as a Bonneville, although I suspect they are.
I'd be willing to part with them. Private Message me if you want to discuss further.