We have three sets of cake steps and three step pads to go under them. We ended up with 2 sets of wedding cake steps and one set of another type that we exchanged our ladder for when we bought the pool. I have a 3 year old and a 4 year old and they both love swimming from one step to the other and having the steps to play on since the whole pool is over their heads.
The step pads were about 3' * 5' and cost about $45 online. They fit nicely under the steps. We did go back and trim them with scissors after they were placed under the steps so there was no extra pad hanging out for the automitic cleaner to get hung up on. It is nice having them because I don't worry about the liner being rubbed by the steps.
When you are looking for the steps, make sure you notice the difference between the sizes of the steps. The two wedding cake steps we have are much nicer (to me). They are white, wider, and smoother. The other step (I don't know the name of it, sorry) is blue, has skinnier steps, and has a rough texture as well as raised ridges (I guess for traction?). Stepping on those steps hurts my feet so I am glad that is just an extra set and not the ones I use to enter the pool. I also think that if I sit on them that they might snag my bathing suit. I have no comcerns about the white wedding cake steps though.
Good luck in your hunt!