For interior plastics, you can use Krylon Fusion "Satin" Black but it has a rather glossy finish despite its name. AFAIK
, Fusion is not made in flat black. If you want a semi-gloss finish, the Fusion is a good choice.
I wanted something closer to flat black. In house paint, it is called "egg shell" finish and is in between flat and satin. I got good results using Dupli-Color Black Trim Paint #TP70. Mar-Hyde Black Satin Automotive Trim Coating #3811 is very similar. Since they are both trim paints, they are compatible with plastics.