I agree a Raphael would be a good fit, make sure you find some that are big enough not to fit in the Cichlids mouth. (mine are all about a half inch but in a tank alone)
I've got an 8" bullhead , a 5" pictus and a 4" sun cat in a 125 with a large Dempsey,Severin , Leperinus , 5" Oscar and some smaller jewels and they all live happily .
Mature Syndontis (excluding upside down cat) would work. Mine is peaceful untill it gets picked on, then it's out with the knives. Raphael would also do.
I am on my 4th catfish with a 5 inch Oscar. I don't really know what kind of fish this is other than it is some kind of synodontis. I picked it up at a Meijer store on a whim for five bucks. It is a tough little customer, about 4 inches long. He will swim around the Oscar and even eat food specks off the side of it when the Oscar blows chunks out his gills.