I believe that the 550 came in DY in 87-89. *It was later reissued back in 1999.
You can get a new authentic
Ibanez neck plate from your local
Ibanez dealer, although it would probably make more sense to just buy an All Parts (or some other part supplier) neck plate from your local guitar store.
You can also try to remove the remaining finish from the neck plate, and refinish it yourself using "Rustoleum" spray paints, which are durable, and designed to endure "abuse."