Sorry guys - Nissan said the exact name was "Engine Oil Filter Adaptor Gasket".
I had no idea what it was called when I rang them, took me ages to explain it but it is definitely the o-ring on the other side of the oil filter. I find it hard to explain where it is but to get to it you remove the oil filter, unbolt the part the filter screws into and it's on the back. It's orange, mine failed. The only reference to it I could find on here was someone saying they had to replace the orange o-ring but never any part #s mentioned.
It does look almost identical in size to the oil filter gasket (rubber one) but I'm not sure if I am game to just take one from a filter unless someone else has first, heh. Apparently it's common for it to fail on VQ engines @ around 180k and I'm just over 200k.