Bankruptcy Judge Christopher Klein appointed Bankruptcy Judge Elizabeth L. Perris as mediator in the Stockton, Calif. chapter 9 case and ordered the city and its creditors to meet with her next month, Bloomberg News reported yesterday. Judge Perris will hold a conference on Aug. 30 in Sacramento to decide how to organize the mediation, Judge Klein said in an order yesterday. Judge Perris was named mediator two days after a group of retirees filed a lawsuit in an effort to stop the city from cutting off their health benefits.