Steps or ladder?
I haven't found much useful among accessory ladders at RV dealers, know some people carry small step ladders. Most things that look and work really neat are custom-made, whether original equipment in RVs and boats, or aftermarket.
If you have an idea about how you want it to work, but don't think you can build it yourself, take your idea to a cabinet shop or a custom boat builder. What you'll get will most likely be wooden, and well finished.
Tom Test
Itasca Spirit 29B