I'm guessing that your tastes are a bit more classic vocal jazz oriented than the faster tracks I recommended in the last post; however, I did suggest a Blossom Dearie track, I'm not sure if you got to that one, but I think she's a classic. Her piano playing gets forgotten by her unique vocal style, she's a bit stealthy with her musical powers and that's rewarding when it shines through. A vocalists that is more "upfront" with her musical powers is Anita O'day.
I'd second the Nina Simone recommendation as well. The "Little Girl Blue" album is her first, she's in her 20s, but the LP is a classic. Like Blossom Dearie it's hard to remember that Nina Simone's is playing the piano as well as singing because the vocals are so commanding. I do hope you find what you are looking for.