Where to buy a seat adjustment switch???

It could also be the power seat motor, try unbolting your seat to clean and lube all the rails and rods. Mine went out on me not too long ago. If you're sure it's the switch, try looking at the junkyards, they will most likely come with the seat, it is just connected by two screws. you can also use the earlier 94-98 years as they use the same joystick including some of the non GT's also. hope that helps.