These are mostly held by Idriess' grandchildren but the following titles are owned by ETT Imprint:Flynn of the InlandNemarlukThe Red ChiefHorrie the Wog DogThe Desert Column.
I hear that film rights for The Red Chief have been sold, as has Flynn of the Inland for a major film in 2018.
Nemarluk is out as an eBook as well as print world-wide
https://www.amazon.com/Nemarluk-Ion-Idriess/dp/1925416569
The Red Chief out now in both paperback and ebook
https://www.amazon.com/Red-Chief-Ion-Idriess/dp/1925416240/ref=sr_1_6?s=books&ie=UTF8&qid=1491092175&sr=1-6&keywords=ion+idriess
The Desert Column - with a new intro by Ross Coulthart - out now in both eBook and print editions
https://www.amazon.com/Desert-Column-Ion-Idriess/dp/1925416879/ref=sr_1_5?s=books&ie=UTF8&qid=1491092175&sr=1-5&keywords=ion+idriess