Robert Beckman mentions having used his own custom bars up to 60 cm wide.
I think the widest commercial bars are 48 cm from Nitto.
There was something by Wilderness called Dirt drops that are designed to provided added control for those wanting to use drops on an MTB where leverage is an issue. They appear to have been much loved by the few people that bought them... Here is a URL -
http://www.rivendellbicycles.com/htm...atlantis2.html
I'm not a fan of moustache configuration bars so I am not sure if these really are drops or somewhere between regular wide, flat, bars and drops.
I started several threads on making chromoly bars, and got some interesting answers, though none to the touring point. I'm pressing ahead with my hopes to make my own bars. But it's one of many projects that may or may not really happen.
I'm real wide in the shoulders and I have 44 or 46 cm bars depending on whether one measures from maximum centerline or OAW. I don't find they are uncomfortable, and if you end up touring in the wind you want to hide as much as possible... I have ridden my 700c bike on some sandy trails and did not like the control of the narrow bars almost as though some clip on bars to the side would have been an aid...
I'm sure this doesn't apply here, but one sees some really unsafe and not effective stuff relative to bars. Compare the kind of person who isn't comfortable on their bike and is riding with their body braced to the bars, wants a wide platform for comfort, to someone who has bent arms is a little tucked (even if they are in a touring upright position, has a supple movement with the bars. On any longer tours even a couch potato will probably morph into proper bar use as the body adapts.