There is a place in Wisconsin that has hoops of different kinds.
2805 East Progress Drive
West Bend, WI 53095
As far as online fabric stores, I think my favorite one is
Ann's Fabric and Crafts in New Hampshire. The pictures of the fabric are good sized and I like their prices.
On the 100 x 100 with fat quarters, I figured that about 26 1/2 would equal that, but that is before sewing. I would get at least 32. Someone with better math skills than me might be able to call it more closely.