I asked the same question this past winter.
I found black rubber pads at Harbor Freight. They were exactly the right width for the stairs, I had to trim them down just a bit.
They look scary, but the nobs are fairly soft and I walk up and down them all the time in bare feet. In sneakers they are GREAT!
--- My ladder kept slipping off the brass holders when I first bought the boat. When I redid the interior wood, I made a new backstop for the ladder. I routed out the back and counter sunk two pieces of 1/8" stainless steel plate on the back before redrilling the holes for the brass brackets.
Unfortunately, I either followed the old piece too closely and created the same flaw or the bracket system couldn't hold my weight... I installed 2 brass door hinges on the floor to keep the ladder in place. All I have to do is knock out the pins and the ladder comes out. Not pretty, but the ladder stays put!
Good luck!
Chris