Am looking for the larger (STi?) hood scoop that will fit into the 2003 wrx hood, (replacing the puny one that comes stock), without any modification other than re-paint. First, is there such an animal and second, where can I find it?

you need the jdm scoop I believe.

http://www.gruppe-s.com/Subaru/subext.htm

unpainted seems to be $140 and painted is $200.