Check out Jenny's in Fountain Valley:
http://www.yellowpages.com/fountain-...abrics-4486553
At the back of the store they have flannel folds for $3.49/yard. It is piled high but worth looking through and stocking up on. They also have cotton fabric folds for $2.49/yard. They also have tons more of flannel in other parts of the store. It's a bit overwhelming but you should be able to find what you need.
There is also M & L Fabrics in Anaheim that also has tons of fabrics. I haven't been there but I hear it's much larger than Jenny's.