The only wide fabric my Jo Ann has consitantly is muslin , they do have a few others from time to time but the variety is just not there and the last time I checked it out it was not very good quality.
I suggest FAbric .com or Thousands of bolts ( at Thousands of bolts do use their search feature called find a fabric) these are the two I use both are pretty quick at delivery. Fabric . com has free shipping at $35.00 purchase so I usually get two backings for the free shipping. Also do a coupon search for them you can typically find one for at least an extra 15 % .. and the coupon discount does not count against the mimium for free shipping.