I just did a ton of research and thought I'd share
The manual calls for "3-bond 1209" but it appears its very hard to get anymore. Some BMW dealerships are using Hylomar Universal Blue instead. I have yet to see an official document from BMW on this though.
Hylomar was bought by Permatex.
The product descriptions for Permatex Ultra Rubber Gasket Sealant (#85409) is nearly identical to Hylomar Universal Blue.
In my opinion, using the Permatex 85409 is the best solution here to ensure long seal life and lowest chance of leaks.