Synodontis nigriventris is the dwarf upside down catfish. This fish prefers soft water, and isn't as robust as many other species, with very mixed results with aggressive cichlids such as mbuna.
The true lace catfish is Synodontis nigrita. It does fairly well with mbuna.
In my opinion, the best Synodontis with mbuna are multipunctatus, or eupterus, in terms of typical availability and price. I've kept Syno. brichardi, and to be honest had mixed results with mbuna, and they aren't that available. Great Syno though.
Pictus cats can work with Haps, but again a mixed result in with mbuna, as their softer skin can easily be damaged by mbuna.