If you're looking for just a block pattern (not a whole quilt):
CompuQuilt has one with the set-in Y seam that uses templates:
http://67.20.92.103/atticwindows.html
Be sure to click on the item labeled Nine Inch Template Attic Window.
And Quiltaholic has one without the Y seam (uses the half square triangle instead) called Easy Attic Windows at:
http://www.quiltaholics.com/bom/attwin.htm