There are a number of toyhauler options that would fit a 13' vehicle. What's your tow vehicle? It sounds like you're OK with an open garage vs separate... Are you trying to keep it under a certain length?
However, I don't think I've ever seen a toyhauler with a rear bedroom as the main bedroom. Some garages have drop down/fold down beds in them but I wouldn't call that the main bedroom. Majority of them have front bedroom, then living/kitchen area, and all have the garage in the back. I think I've only seen one or two that have the living room in the front and the bedroom in the middle, and they're monster size trailers.