Thanks for the suggestions, Janet and Sarah. It turns out Costo, Safeway, Albertson's, Whole Foods, and Cala / Bell were a bust. I was near Berkeley Bowl - and I scored! Seems that a slab of only 3 ribs is the biggest that will fit my skillet. I seared it on both side and finished it off in the oven at 285 F for 4.5 hours. Yuuum!