just think, roughly 90 degrees south, along the axis of the americas, that's the projection

there is a whole bunch of magnetic anomaly measurements that exist also, they put the new poles at around the same location for the north and somewhere mid pacific for the south, around south eastern china or so

probably would help to have a spherical world map to visualise it, or possibly you can find a planar projection that you can get it to orient in the intended direction, and then perform a smear blur over 90 degrees (so it would overlap half way up the other side) and then wrap it back on a globe and see what places don't get totally smeared out

unfortunately i am pretty sure it's nowhere, and certainly not convenient for contemporary geopolitics

i'm going with the high ground theory, and i'll be persuaded to mongolia if my preferred option of midwest doesn't pan out