You can find information about the Gold and Gold Leaf Plus brushes from here:
Downloads for Painter 12.1 or later follow:
Edit: I had a request to furnish my gold leaf gradients. I have no problem doing that. PC users should have no problems installing, but Mac users may. There was a problem for Mac users; they couldn’t import a media library from a PC user. I do not know if it is still a problem. David Gell has provided a script that will allow import of media libraries from a PC user to a Mac. I am providing a link to Painter Factory where you can learn how to use the script and download it.
Please let me know if this doesn’t work for you.