Some of the mens' totes are huge, like 16 or 18 inches, but those would be mostly newer styles (meaning the last 10 or 12 years). There were a couple of good-sized Soho / Lightweight totes from the early 1990s though, the Light Tote style 4065 is listed as 16x13 inches, and the Soho Bag 4082 is listed as 17x15 inches - thats probably one of the biggest leather ones made as a womens' handbag. There was also a dressier Park Tote style 4129 from the 1993 Manhattan Collection. The lighter leathers are probably the way to go since a tote that size made of the thicker glove-tanned cowhide would be pretty heavy. If you're looking for a newer style maybe someone else can suggest some.
Those can be hard to find since most of them were probably made before 1994 when the style number started being used in the serial number, but both styles did carry over into 1994 and maybe a bit later so a search using the style numbers might still find a few. Or just search for
Coach Large vintage tote. I'll include a pic of the Soho Bag on a model so you can get an idea of the actual size since the bottom was boxy and much narrower than at the top (and probably not as useful if you're carrying something oversized, like a full-size laptop.