I have heard of freshwater lion fish but they are usually called scorpionfish. they are actually brackish water fish but can be kept in freshwater and saltwater. I heard of someone keeping one with mbuna cichlids. They are carnivores and eat anything that will fit in their mouth.
There scientific name is allenbatrachus.
I have never kept them but i have read about them.
The only thing i can think of that may be called a FW lionfish would be species from the Vespicula family, these are a group of poisenous predators from the perch family but information on the is scarce if not non existent.