I have used other Uruguayan cichlids of the genus Australoheros, and Crenicichla, and high altitude Mexican live bearers such as Xenatoca.
Buenos Aires tetras would also be appropriate.
Australoheros sp red ceibal
Crenicichla saxatilus cardozo
Xenatoca eiseni
others not as geographically correct, but could handle cooler waters might be white cloud mountain minnows, rosey barbs, or Macropodus opercularis.