I think they are around 90 bucks or so, contact kingofparts they can hook you up.
Btw, I did this today, changed the plugs out for 1 step colder ... I made a booboo though, the plug that plugs back into the coil pack. I broke the little tab off ... oops. I called subaru, and they only sell the whole engine wiring harness ... like 300 bucks ... so I wrapped the plug in black tape .. it seems to be pretty snug ... so time will tell I guess ... I need to find a junked car and cut the plug off