Now, to inform the OP.
Few rear beds are oriented sideways in B+ rigs. If you want used, look at Born Free Bed and Breakfast (rare), one long Born Frees had rear twins that likely make into a king, some Rialtas.
New...Pleasureway Pursuit.
Many Class Bs give what you want. Sportsmobile will do a sideways bed install in a B.
In a Class C, many longer ones have a rear queen that is lengthwise, and some newer ones have a rear side slide with a queen. Lazy Daze has a nice rear dinette model C.
For a few big $$s, LTV makes a nice B+ rear lengthwise queen.
