I'd say it's actually a Macrospilus.
They're the common variety found in most stores.
The affinis is also known as the "dwarf" or "golden" oto. It typically has a golden sheen to it, and the black stripe is much less defined.
The vittatus is a much more similar fish, but doesn't have the spot at the base of the dorsal fin, and the white stripe is much more defined and solid.
So, yeah. Because it's not gold, and because the white is not solid, and because the black branches out, I'm going with the Mac.