Rear Bumper / Blind Spot Sensor replacement

Relatively new member here. Have had my Tacoma TRD Off-Road for about a year now and totally love it.

I have had a recent issue with the BSM system. A few months ago it just shut off and said "Blind Spot Monitoring Not Available." Dealer told me that the bumper had been hit and the sensor was off by 14 degrees and couldn't be re-calibrated until the bumper was fixed.

I have taken the whole left side bumper apart to inspect - there is very minor damage to the painted cover and hard plastic bumper underneath (the piece to which the sensor actually mounts). None of the damage is anywhere near the sensor itself, and even after measuring (compared to the right side), I can't see any major alignment differences.

Since the dealer won't re-calibrate it until the bumper is fixed, I feel like the hard plastic bumper (not sure what this is called, but it is where the sensor is actually mounted) needs to be replaced as that is what is holding the sensor into place.

Has anyone had experience with this? Do I really need to replace the mount to get the sensor realigned? If so, has anyone replaced just this one piece? It appears to be Toyota part number 5215404010. I can probably replace it myself - really trying to avoid a trip to a body shop to do this; I know either way I'll end up paying to have the system re-calibrated.

Any advice is very much appreciated!