G'day mate.
I'm not worried about 'advertising' on PPRuNe, and someone else may find this useful. Doing an ATPL flight test privately is not all that common, and as you will know it has to be done in an aircraft of reasonable complexity and performance.
Air Wanganui is probably your best bet. They've done this sort of thing before using their Piper Mojave.
Do you already have an ICAO ATPL? I'm sure you've exhausted all avenues, but it could actually be easier (and would certainly be cheaper) to do an Aussie ATPL and convert (no flight test, just convert your license, and do the papers).
Perhaps other people have got more options........
Good luck with it all
