“Rusted”? No Magearna was rusted, at most paintless.
The one given in HOME wasn’t rusted, it is “Original Color”: the paintwork that was adorned on it 500 years ago in Pokémon world. It’s neither shiny nor rusted.
That aside, shiny Magearna was never released. I can’t make heads or tails with what you’re describing. I think you misunderstanding something fundamental about what was released and it’s form names
In any case, we already have the file uploaded, no need to recreate it. (Unless you’re talking about the bugged version, of course)