I've never bought OEM levers but most aftermarket levers will come with the perch you are referring to. I would think OEM would include the same piece. However, I bet someone on this forum still has the oem levers that they have replaced and would give you a good price. Try posting in the wanted section..
That highlighted tab area is for activating the brake light switch. It is not separate. There's no part number for that because you can't buy it separately. The lever is 1 piece. Aftermarket and OEM are the same way.