I went through the same search when trying to find a replacement ladder for my Catalina 25. None of the easy available options seemed like they would work very well and I wasted a couple of hours searching catalogs and looking at options.
The good news is that Catalina Direct started offering the C-25 ladder design again, and it is a very easy one to retrofit to other boats with a near vertical transom.
Catalina Direct: Transom Swim LadderCP-18, CP-22, C-25, C-27
When folded up the bottom rung should be near the stern pulpit rail level. When folded down the bottom rung is in the water, with the other 3 going up the stern.
I recommend securing the ladder using a line tied with a slip knot that can be reached from the water. That way the ladder can be deployed from the water if something goes wrong.