At least one species of bumblebee catfish is in that size range, not sure which one it is though.
Some of the Doradidae (aka "talking" catfish) as well; striped or spotted raphaels are the most commonly available species.
Banjo cats also come to mind, along with the ones already mentioned above.
Synodontis nigriventris, the common upside-down catfish, max out around 4".
Synodontis are the most likely to be visible by day, at least if kept in a group.