There's a nice compilation CD called "Violin sing the blues for me"(Old Hat CD1002) that's got a lot of early blues fiddle numbers. The great guitarist Lonnie Johnson recorded a few fiddle tracks as well.You'll have a lot of fun listening to the Memphis Jug Band or the Mobile Strugglers.
   But in the end I doubt if you'll find any blues fiddlers getting within miles of the guitar/singer greats, and the harmonica was always the successful alternative to the guitar,the fiddle never got near. Odd, really, becaues the fidddle would seem to be ideal for the job. Fashion, I suppose. The fiddle was essentially old-fashioned in black musical circles 1920-1940, and just not cool enough to be taken up by the right people. A shame, perhaps.