What year GT?
Mid 2001 and up the front brakes are the same as a GTS. A slotted/drilled rotor will make no difference in the size of the brakes. Only bigger brakes do that, and if that were an option for you ($1000+) I doubt you would still be running 15" wheels.
So, I imagine lots of people make the rotors you are looking for. I just can't imagine why you'd want them...
Scott