Yep,
Thunderguts you are correct! I don't know how I missed that.
#577 and #747 are parts no longer made and superceeded by p/n 18102208804.
Look around for 18102208804 on the interwebs. But it also looks like #804 is no longer offered by BMW. ?
I found it for sale at
Leebmann24.de (over here in Germany) for 585,19 €, that is about ~$685 USd. They don't have it in stock but that just means they can order one from BMW AG.
https://www.leebmann24.de/schalldaem...102208804.html
and for 665 € euros here...
https://www.baum-bmwshop24.de/bmw-sc...m-18102208804/
Found one in the states for $614...
https://www.bmwpartswarehouse.com/AC...-43029-acc.htm
Good Luck,
Dackel