Couple different options- wait until someone post one for sale or replies they have one. You can pick up a used one sometimes for a good price.
Plasti-dip. Be careful not to get fuel on it as it will ruin the dip.
Paint. This was a method I chose and I like the outcome. I know some have used bed armor truck bed coating. I prefer a none textured appearance.
Drake makes a nice fuel door for about $175. Check out speedlogix.