Why don't you tell us who he is?
What is the point of leaks if you just tease people with the information?
I don't see what is to be gained; either keep the information to yourself, or share it in full. If you just want to say, post-reveal, 'I was right, I told you X was Y' then we'll just be saying 'well not really, you just gave as vague a description as possible.'
Why does your friend care what you say about KOL? It's not like, assuming it's legit, that he can be pinpointed as the only source.