2002 Z3 E36 Sport 3.0i siren issue

[KingDustbin130]

Hi, looking for some help please. I have a 2002 Z3 E36 Sport 3.0i. The siren has caused my alarm to go off, so I am told I need a replacement siren. Mine has a battery backup, but I am unsure where to find the battery, BMW states both discontinued parts. Would a secondhand siren from another BMW model without battery backup work? Not sure if that would work. Mine has 4-pin plug at the front of the siren.
My Auto Electrition guys have told me this information but draw a blank about the above questions.
Help Required!

 

[Geoff Crispin]

You might find somn help logging onto Resources on this site where there is lots of tec help

 

[KingDustbin130]

Thanks.