Part number for the center hub cap for style 5 wheels is...
# 36-13-1-181-068
The emblem # is 36-13-1-181-079, you might check if new caps come with new emblems installed.
You'll need a wrench to remove them, part # 36-13-1-180-626. Align the arrow when installing them, they just pop in place.
Your nearest BMW dealer should be able to order these for you, or might even have them in stock.
Good luck with the 5's...
Jr