From my personal fabric stash. I bought this at Mood Fabrics in NYC. 

I am a Project Runway fan and so I had to see Mood Fabrics. Incredible place. 

5 yard bundle of Unbleached 45" Cotton Muslin

Product # 305201

A plain, natural beige surface with flecks of darker brown provides a simple, barely textured base that won't detract from design details, while a crisp, malleable drape makes this muslin ideal for draping patterns, making mockups, and, occasionally, lining garments. The size of this bundle provided plenty of material for most projects.