While we have touchup available on our site for various finishes it is just for small scratches and chips not for repainting the furniture. Your furniture was originally powder coated and then in some cases hand finished.
You could consider having the furniture re-powder coated. A local dealer may be able to assist you in finding a company that would provide that service. Other people have had good luck with a light sanding and painting with Rust-Oleum paint. The most popular color seems to be a semi-gloss black.