P0430 is either a dead / dying catalytic converter or a dead / dying secondary O2 sensor on that cat. A competent mechanic should be able to deal with either of those conditions. If the cat needs to be replaced my preference would be to go OEM; but, an independent mechanic can source an OEM cat easily as long as you make it clear that is what you want.
In reality, if you can find a shop that specializes in diagnosing emission compliance issues might be the best choice. You don't want the mechanic replacing the cat if the sensor is the problem.