The Newmar Allstar model 3950 and 3951 has a loft. It has a queen bed and over the queen bed it has 2 twin beds. It is a very neat floor plan. They also make a model 3954 that has bunks as well as a queen bed. I don't know of any that has just twin beds. Good luck.
I actually test drove the Allstar model 3951. I was very impressed with the amount of room that it had in the back. I could stand flat footed in the master and had several inches of head clearance. Good luck with your search. If you are only looking for a gas model there are several class A that have bunk beds. If you are interested let me know and I will list some of the ones I have looked at. We were looking for a class a that would sleep more than normal so my wife and I looked at a ton of units to find the right one for us.
Haha, I'm having the exact opposite problem... I'm looking for a full/queen bed, and I often seem to find twin bed setups. But that's on older models (late 80's, early 90's) that I'm shopping for, and I'm guessing you are in the market for a newer rig. At some point, manufacturers must have realized that spouses like to sleep *together* so they ditched the twin bed idea.