That was an old post. I see you are new - this is a great resource for information - just use the search and you will find almost everything!!
alarm siren was:
Mercedes #A 171 820 25 26 subs to A 219 820 32 26
Chrysler #5124443AB
ECS tuning #ES1779675 /2198203226
https://www.ecstuning.com

search ebay or the net or call around for the current local best price.

the new ones all require an 8mm nut that is not included for mounting
And don't forget you need a security TX30 torx for removal (hole in the centre)
I've done a couple and the hardest part is usually getting the wiper arms off - will probably require a small puller.

And you have a great resource and group in your area NWCrossfireClub https://www.facebook.com/profile.php?id=441428485887343

We even met up for the tractor parade at Christmas in Lynden - make sure you join - lots of local help and runs and info on the big July Run CCAA7 in WA

Welcome and Enjoy!