The majority of the shifter is not considered a serviceable part and thus parts are not sold separately except for the cover and the front display.

You can check eBay for a replacement.
2008 BMW x5 Gear Shifter Selector Switch iDrive Controler CIC | eBay
BMW E70 x5 E71 x6 Genuine M Shifter Trim Shift Knob New 2007 Up | eBay

You could find one that has other damage and use it to repair yours or repair the replacement or buy a functional replacement.