Originally Posted by Dagul
I installed a hitch and wiring harness recently and the "converter box" came with the towing wiring harness kit. ...
Thanks for the confirmation, Dagul! ...
So ... To return to the OP's original question ... Apparently you need to ask the parts department to look up the towing wiring harness kit and see if the converter 'box' is available separately.
I don't recall anyone ever having one of these converter thingies fail before. I'd thoroughly check out the wiring first before finally deciding the box must be bad.