Chasing a spare key 2006 model like this picture

Have you tried gumtree I recall they come and make one for $99 ebay has it as well..

Alternatively ring A1 Locksmith, when I was there last week they had a myraid of keys available. They can even reprogram the key to include the central locking buttons to function etc too for $265 brand new, much cheaper than quoted $600 from Subaru Dealership.

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Subaru WRX 2005, 2.0L