There was (still is?) a company called Flexible Drive Agencies, they make push/pull cables for such applications. They were in Alice Street Newtown, not sure now. But they can make a custom cable, lockable even, for these. I had one made for the PTO on my series.
Here:
Home - Flexible Drive Agencies Pty. Ltd
Probably the place to start.
FDA Push-Pull Cables - Dash Controls - Flexible Drive Agencies Pty. Ltd

