Steam shower lights vary in size, mounting, brightness and voltage. I would have your client look at the various in-shower and steam shower light fixtures available here http://www.steamsaunabath.com/steam-shower-lighting.html
. These are the best steam shower lights available.
As for an in-shower light switch, Bathology is the only brand that we are aware of. This light switch can be mounted inside the shower and will turn the light on and off as well as dim it. Additionally, the switch has a built in 20-minute countdown timer so the light could never be left on for very long. Here is a link to this shower light switch http://www.steamsaunabath.com/catalog/in-shower-light-switch-with-on-off-dim-bathology-p-301430.html