It's in the book Dereliction of Duty, by Col Buzz Patterson (USAF ret.). He was one of the servicemen who carried the nuclear football wherever Willard went.
Hillary's 'plastic box of secrets' was part of a retelling of a trip on Marine One. Basically she would let no one touch it - even though she treated the WH Military Aides as butlers, valets and luggage jockeys, and that it never, ever left her side.
The local library should have the book.
And when done reading it for one you'll see there was more reasons than just perjury to impeach his sorry behind (he really did lose the launch codes). Secondly they both do loathe the military, especially Hitlery.
Any speculation as to what it contained.