Possum, I don’t think there is one. At one stage I know people were making their own with Ozzie Explorer but that fizzled out when Ozrunways provided such a cheap alternative.
i used the AirNav product for years before iPads became common. I changed to iPads with Ozrunways in the Auster about 5 years ago and regularly travel across much of the country without any problems using it.
I no longer spend a fortune on the required paperwork, I have all the current charts at my fingertips, I lock the screen to avoid finger problems and the map automatically self-centres. It provides me with ground speed, ETR, frequency changes and a heap more. I’ve never had a failure but carry a back-up. I can get NOTAMS, weather overview, and other useful information on the wing and call a taxi and motel when I arrive.
While the gps is not approved and I am old-fashioned enough to enjoy map-reading, I continue to be amazed at the accuracy of the iPad gps. And I’m a Warbird, too.
I would never go back to to Air Nav. Time to change, mate.
kaz