I did a Google search on "fabric 95% cotton 5% lycra" and got quite a few hits; not sure if all of them are reliable. However, I did find this category on fabric.com that seems to meet your requirements:
https://www.fabric.com/apparel-fashi...ra-fabric.aspx
Edit: Note that some of the fabrics there are polyester instead of cotton. I think you will get more hits if you Google "cotton jersey fabric" as that seems to be the cotton/lycra combo.
Edit2: You may find more variety and better prices on eBay:
http://www.ebay.com/bhp/cotton-spandex-fabric