I'm fat and I'm going to be doing a lot of walking, what shoes would you recommend?

Pretty much explains itself, but I’ll be spending the better part of 6 days walking, and my feet hurt as it is, probably because I weigh about twice as much as I should. I also have no arch whatsoever, the flattest feet you’ve ever seen. Right now none of my shoes are all that comfortable to wear for long periods, so I’m thinking if there really are shoes out there designed just for the fat, flat footed person, maybe I should get a pair, damn the cost. Any suggestions?