I looked only at Calphalon for a quick peak. They have pans to 14 inch size. I see what you may be up against. I'm not sure how you get an 18 inch fry pan to evenly heat. Or if it's full, how to carry it from stove to setting on a hot pad at the table without getting all wiggly wobbly.
Try Cabella's (on line) or do you have an REI in Mtn View, or else look at their on-line catalog too. Camping and roughing it in the great outdoors for larger group size meals.
Google Large, extra large and Jumbo Fry pans. ( thank goodness this is cookware and not clothes). But if you find one, check out your waist size before and after
Maybe you could look at electric fry pans. They come in larger sizes.