Roo has a couple for sale or will have soon. I've just sent him some stainless steel mesh to replace the mesh on the filter cover, as soon as he's finished restoring them he said he'd sell a couple. Maybe give him a PM and see?
As for the duct, AFAIK it was only used on the carbs with the 78 main jets, almost impossible to find these days. If you have normal 623B carbs on the 500 or 069A on the 550 you're better off with just the mesh.
