Just to let you know, I have been using fabric store backdrops for years, but locally I have three fabric stores (JoAnn's, Hancock, & Walmart ) and it is very rare when they have anything wider then 60" in stock. If I have to special order the price goes up so much I might as well order a scenic from B+H, which I did. I have to date found one length of fabric that was both wider then 60" (9ft in this case) and useable as a photo backdrop.
The second best choice is sail canvas from marine store specializing in sail boats, but that isn't cheap either around here.
What I have found, but I usually have bad luck with these things.