you can get them in the real big custom sleepers like the 96" and bigger. in stock sleepers the most you will find is sinks in the volvo's. Actually those volco's are getting huge these days. The only thing comperable is the kenworth studio but I'v never looked into one, they are way expensive.
I had a 96" sleeper built for a pete about 10 years ago and there was an option for a toilet and upon considering it I decided that it was kinda nasty and I didn't want it. If you can't take the time to stop and use the can then what's the point! on the other hand I'd love a shower!!! just to save my feet from nasty truck stop showers