You can try getting one from o/s. In my experience it's bound to be about half the price. Do a Google for HKS headgasket, searching in Australia only and you'll see.
I got an HKS metal from cyberauto.com for my 4AGE and it ended up about $250 shipped from memory. Also try Takakaira.com in japan. They are very good and cheaper than in Aus. If they have the part in stock, it will be quick. Otherwise they let you know how long it'll take.
I hope this helps. I am only talking from my own purchasing experience, however.