I replaced the third brake light in our 2008 135i convertible a couple days ago. After reading about having to file the tab and reading the Dorman reviews on Amazon, I figured I would see if I could find a model with the old notched design.
I found this one at carparts.com showed the notch in the pictures:
https://www.carparts.com/third-brake...ent/rb73330001
The install went smoothly and no filing or grinding of the vehicle or the light.