Hi there! I am not a native English speaker, but I recorded the vocal announcements for en_US anyway. If you can bear an accent, this might be of use until a native speaker can record this. :-) I license this under "Creative Commons Attribution 3.0 Unported" (http://creativecommons.org/licenses/by/3.0/). Would be great if you drop me a message if you end up using this.
If I find some time, I might also do a recording for de_DE (German) which is my first language. Just to clarify how to translate this: In what cases would the announcement "turn slightly to the right" be used? Like a street going off in a 45 degree angle or something?