foubnd it, slighly confusing, couldnt see the specific one you mentioned but found 3 possible options:
waterpump on its own: http://www.ebay.co.uk/itm/Nissan-2-4L-KA24E-SOHC-12-Valve-16-Valve-New-Water-Pump-/360321124113?pt=Motors_Car_Truck_Parts_Accessories&hash=item53e4d00711
timing chain...