I would have to order up new from Nissan as it is not a stock item I am afraid.
Nissan are showing them in stock in UK, Amsterdam and Japan.
just give your local Nissan dealership a ring, or @Coz@Torqen
Torqen have them listed; https://www.torqen.uk/nissan/350z/engine/gaskets/1036-350z-de-nissan-oem-vtc-solenoid-gasket-23797-2y50a.html