This is a budget question as much as anything.
For example, our Seattle son has a 1977 Scamp
13 with front bunks. It easily meets the sleeping requirement. The front bunk is easily adequate for a child.
We have a Scamp
16 with front bunks and though we've disabled the upper bunk I regularly lie on the bottom bunk and have actually been caught napping there.
Another interesting solution is a Scamp
19. For some reason I frequently see good deals on these and they can easily sleep four in comfort.
One thing we did before actually getting our Scamp was to attend a Fiberglass Rally
as walk ins. People invited us into their rigs even before the "Shine and Show". At one of these rallies you can see a number of solutions.