how much does the torque conveter for 2006 toyota carolla cost

Question

i took my car to aamco after toyota dealership stated the torque converter was the problem for my car. Aamco claims that it was the torque converter but then 4 months later the car check engine like gives the same code...

I would like to know is there a way to order a torque converter for my car and i also want to know if all previous steps have been done like checking and replacing trasmission fluid what else can be the problem? does the problem have anything to to with the ECM?