I still do, but I didn't know what to search for! But, I managed to Google Gandalf's talk with Pippin, and then was able to find it in the books.
The words Gandalf used were actually taken from the description of what Frodo saw as they sailed into the west after leaving the Grey Havens at the end of ROTK(book).
I dunno, I've been looking through my Word copy of the books, but haven't really found anything suitable to use, imho.
I couldn't think of anything quite appropriate, either. Not for this situation. Maybe it shouldn't have a quote, just a "we're praying for you" message.