I can produce David Porter's statements on the subject, and I think Lincoln's secret orders to Mercer are out there, but to my knowledge, David Porter never released copies of Lincoln's secret orders to him.
David Porter says some of what was in them, but he doesn't provide a transcript.
Now you can either say David Porter is making it up and is a liar, or you can accept what he says about them is true. Which way do you want to go on this?
Lets see Porters statement of the Subject.