Call Brown Roofing in Manassas Virginia. The owner Dave owns a powder coating business, and at least one of his employees there has helped in the past with getting some stuff powder coated. That employees name is Audie. At the very least they should be able to put you in touch with the powder coating shop.
we are not in DC but we are a site sponser and you can rest assured your parts will be done right the first time with us. Everything will be properly masked and the coating work will blow your mind!