I've made several of these in both the 9x13 size and the smaller, round size - both styles - wood handles and rounded, with cloth handles. I attend a fair number of potluck dinners and have used my carriers, and definitely recommend the style with the wooden handles. The handles provide an extra bit of stability to the carrier.
Like you, I searched for a pattern and found mine in McCall's Quilt Quilts November 2005. I've just tried to find a past issue on-line but failed, maybe someone else will have more luck. The pattern is similar to the gotfabric link. Here are a couple of pictures to help you out. I wanted mine to be flannel on the inside, so sandwiched and quilted my fabric before cutting it for the carrier.