The ladder we tried first in the older Class C (5-ft climb) was a "Skinny Mini" that looks a lot like the Cosco versions.
Quality product but not very successful in the cabover bunk application. Nice wide steps but it has to be opened to use, and that made for an extra pair of legs to find a footing for.
You can see both Costo and Skinny Mini on Amazon. A whole lot easier than crawling through the Home Depot web maze.
I got the 5-ft aluminum step ladder I mentioned before from Ace Hardware. The Big Box stores seem to have 4-ft and 6-ft but not 5-ft. I paid more for 5-ft at Ace than 6-ft at Big Box. Walmart probably has them.
