I bought this necklace from a dollar store many yeard ago, sadly the metal started to have green rust and is in bad shape.

Since this aint from a jewelry store, I am not sure on how to proceed to find a necklace with with design. Id like to find a version made of gold/silver/iron that wont erode so easily. Where should I start? Would a custom order be my best bet? (Even tho itd be expensive).