If you have access to Melissa Leapman's
Knitting beyond scarves, there is a simple hat knit flat, (yes, a rectangular garter stitch piece) in that book. But It ends up looking side-to-side and is joined together by attaching the cast on edge to the bind off edge, then weaving your yarn through one of the open sides, gathering tauntly, and rolling up the cuff. It is quite attractive in the picture.
I looked on the internet too, without much luck, but hopefully someone else will have some suggestions.
Good luck