Just did this, took a little extra effort since I have an 08 E92 (no plastic stalk/ lego piece). My method was three fold:
1) Pen cap (acts as a plastic stalk to push the custom flat surface)
2) Pen cap connects to a small cut out credit card square plate (use any old credit card) - cut two squares to fit into the space
3) Sandwich double tape between the two credit card squares, adjust thickness as needed (by adding more double tape. Trail and error until you feel the two rubber buttons are pushed by the switch.
DIYs where you got to think on your feet, get creative = mad FUN!