I'm having great difficulty getting hold of a replacement 2012 Optima rear bumper reversing sensor.
Does your difficulty extend to one or more KIA dealer parts dept? I ask because there's a fair chance that the sensor is common to several different KIA/Hyundai models.
In any event, perhaps if you were to contact the KIA Customer Support group in the forum, with details of your model, (VIN number) they might be able to assist. Another alternative is to sound out online breakers.
My apologies, 'Yicker', if you have already been there.
'Jack Daniels' has suggested 'Partsouq' and while I have never had occasion to use them myself, I am aware that there have been several instances previously within the various sub-forums of members recommending the company.