Yamaha psr e343 battery port change

I think you may struggle to buy just the battery port but if you manage to pry it out you could clean it with rust remover and a wire brush and restore it to a good condition. These parts are normally just some nickel coated plates and springs.

I would try to carefully pry them out of their socket (might need to take them out from the underside though) and then soak them in rust remover, then give them a good scrub with a wire brush. Sometimes you can use finer grit sandpaper to remove the corrosion.