also this
BMW E53 X5 PDC SENSOR ULTRASONIC FRONT PARKING DISTANCE CONTROL 66216938736 | eBay

The first link is the piece for the center of the bumper, the second is for the sides. I'm not sure if they're side dependent though.

Hi there, you ever get this damage to the case sorted out? was the sensor attached to the bumper via a casing that is pre-moulded to the bumper out of curiosity? i buggered a center sensor and it plays quite freely in the bumper hole, would prefer to have the mouldings to hand in case it case they are needed once i try to get a new sensor in...failing that am gonna see if anything can be salvaged with a strong glue to keep that housing snug to the bumber and hence the sensor in it..cheers

Right I can confrim above as after a few hours & with the help of my father in law who was breathing down my neck and in hurry to help me...this 'part' or housing for the pdc sensor comes affixed to the bumper for my facelift 3.0d at least...I tried to force it back into place after we removed the bumper but it wouldn't securely clip back on, so I used some of this and then pushed it into place and hoping it actually holds Adhesives, Applicators, Heat, & Glue Guns | Caulk, Sealants, & Adhesives | VersaChem® Plastic Welding, 47809, 25ml Syringe | B967552 - GlobalIndustrial.com

the plastic welder glue i used apparently doesn't work on P/E PP plastics...BUT somehow is holding I think assisted by the fact that the housing for the sensor wedges in place under the styrofoam that is on the inside of the bumper....still be good to know if this sensor housing is detachable or not as judging by the looks if mine wheni had it out seems it was fused in the 4 corners to the bumper