98 a6 tail light problem
 

i have a 98 a6 and when i bought the car every time i hit the brake it makes a loud beep and i noticed the center tail light was out so i went to look at it to replace it and the whole thing is gone, no lense, no socket for the light bulb just the plug thats hanging and im looking all over online to buy a new light but i cant seem to find one so if anyone knows where a website is that sells the center light that would be awesome because this beeping is driving me crazy!!