You can get a "universal" 02-07 kit on ebay for around $60. I got one when I put on my STI intercooler. You'll have to do a bit of trimming here and there, but it worked for me.
A word of warning that the silver gaskets that come with it are crap. You'll want to pick up the black paper gaskets from Subaru or a local shop for a few bucks. I had a boost test done at a local shop after I installed it and the silver gaskets were leaking at boost above 15psi.