I just tested the German – Standard layout on a Mac, it's the first one you indicate. Apple calls right-⌥ the Compose key, not AltGr, but works the same way, other than being transposed with the Command key from the familiar Windows style of layout.

There's also a keyboard layout just called German, maybe that one works the way you refer to? But surely it's not too much to ask that someone select the keyboard style they're accustomed to using?