The siren can be replaced with one of two replacements, both beep when the car is locked or unlocked. One is held on like the original using the stud and the other uses a 8 mm screw in place of the stud. I used the one that uses the screw.
The two electrical sockets on them are identical to the original. Both of these are still available, order it using the Mercedes part number, never order it by the Chrysler number it will either be out of stock or a smarter parts supplier will sell you one of the Mercedes parts with a large price mark up.
Facebook is not as good as the CrossFireForum.org for part numbers, so go there for part numbers and posts on how to do the job.