You can try Mapleshades' excellent recording "Country Girl" by John Dee & Fris: Voice and guitar with some electric piano sprinkled around.
I also recommend Doug MacLeod "You Can't Take My Blues" on the Audioquest lable. It has a little more accompaniment, as does the above mentioned Muddy Waters, but the main focus is always the voice.
John Lee Hooker is also excellent, but recording quality and number of players varies.
And remember: "If you don't like the Blues, you have a hole in your soul".
Have fun, Ed