I was missing one when I bought the F22. I couldn't find a part number either but found it on the F30. same part, called a bearing cap. got one from Amazon:
BMW Genuine Front Axle Suspension Wheel Bearing Cap 740i 750i 750iX ALPINA B7 ALPINA B7X 740i 750i 750iX ALPINA B7 ALPINA B7X 740Li 750Li 750LiX 760Li ALPINA B7L ALPINA B7LX 740LdX 740Li 740LiX 750Li
https://www.amazon.com/dp/B01JEG0ANM..._O7WlDb1FTR9QY