I'm interested also. I have a very old stepstool and a foot on the sink but won't allow my wife to sleep up top because the set-up is too dicy for her so she sleeps down stairs.
As mentioned earlier. I had Kenny at Aluminess build one of these for us. (wife loves it for getting up and down in the middle of the night) I am not the originator, saw it at Aluminess and simply asked him/them to build me one. I am certain he has a file on them? Small and pretty light but rugged, fits perfectly behind driver seat and top lip rests firmly on top edge of penthouse bed. I use a few suction mounts to secure it when not in use.