Thank you for contacting Slingbox Forum. I am sorry you are having trouble in locating a remote for your Australian Foxtel TDS851NF box.
You are able to search and request a remote at the Forums at answers.slingbox.com. You will go to Forums and looking down the right side of the page find Remote Control Request in the Have a great idea for us? section. An article will populate with the information you need.
Hope this helps with your issue!
Have a great day!
Sling Moderation Team