OK, I did some more research on this.
seems there IS such a filter!
it requires removing the "seatback board". the filter is attached directly to the climate controlled seat blower motor.
took a screenshot (pardon the quality)of the clips/pawls that need to be accessed to remove the seatback.
bear in mind this is for a 2012 qx. the 2017/18 armada should be the same.
EDIT: theres TWO filters per seat: one for the seatback (for your back) and one for the sleat cushion.
both are circular, according to the service manual exploded view.
so it seems , based on petites link, there's different designs.
since the armada and qx are based on the patrol and are made on the same line in japan, it makes compelling speculation that the filters are circular and not square.
since the op has an armada, op should contact nissan and ask for the part number for the seat cushion blower motor filter, and we can cross reference from there.
Last edited by marctronixx; 05-26-2018 at 03:19 PM.