Rockauto.com is your friend. I think I used a Legacy's valve cover gasket.
I'll check to see if they have a purchase history option and let you know what I picked. Don't forget the donut gaskets and the ones for around the spark plug holes.
Edit: This one:https://www.rockauto.com/catalog/moreinfo.php?pk=3602967
The Beck/Arnley® brand is a leading specialty supplier of premium, quality import parts that meet OE performance for foreign nameplate vehicles.
State of the art manufacturing to OE specifications for a precise fit
Engineered from premium materials to provide exceptional service life and reliability
Designed to withstand the harsh conditions in the modern engine compartment
Alternate/OEM Part Number(s): 11051AA070, 13271AA071, 13272AA094, 13293AA051, JN3012L
Edit#2: Make sure to get the correct right or left side one