No, if you have a standard size queen bed, any standard queen sheets should work.
However, there are short sheets you can buy for the short queen size bed in some (many?) RVs. Check out RV suppliers, like Camping World. They tend to be low grade, and more expensive than low grade sheets should be, but the law of supply and demand says otherwise...
There's always scissors and a sewing machine! :clown:
Actually, what we do is keep a "twin size" blow-up mattress around. It has a built-in battery powered pump. That goes on the "sofa" that unfolds flat. It makes the "sofa" comfortable to sleep on for short people, and the pump reverses to take the air out for storage. Quick and easy.
42 by 72 is larger than a twin, but smaller than a double. I would used double sheets and tuck in the extra. The dinette, 38 by 68 is the width of a twin bed. Twin beds are usually around 39-40 inches wide. Just use twin sheets. Of course they will all probably be too long, just tuck in the extra. On my short queen, I sewed the top to the bottom sheet and there is a good amount of elastic on the bottom, and I have a 3 inch memory foam topper that the sheets fit nice.
Sheets are quite easy to make. They are also quite easy to remake on a sewing machine.
Camping World has some sheets for the short queen. On the package, the manufacturer claims to 'have 15 colors, 7 different thread counts and make custom sizes'. You might check them out to see if they can provide what you want.