The original cab bunk ladder Jayco supplied with my Seneca was very uncomfortable to climb in bare feet, even my young grandsons complained. I purchased an aftermarket RV bunk ladder from Amazon, it had wider rubber-covered rungs, but was flimsy and still hard on the feet.
I recently decided I needed to do something better. So I sourced a "shelf ladder" from Amazon which is somewhat like half a stepladder. I then fabricated two adapters out of 1/8' steel stock. I riveted these adapters to the outer beams, and the top of the adapters were heated and bent to form hooks for attaching to the existing bunk. I then painted the whole ladder in black textured finish.
New ladder is very sturdy, no deflection at all. And the rungs don't hurt the feet! I still may cover the rungs in carpet so they are not are not so cold.
Here is the Amazon link for the ladder: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Below is a picture of the finished product.