Rolling Safety Ladder

Rolling Safety Ladder
I strikes me that I should get one of these for access to the eyepiece on the telescope. A conventional step ladder has no rails, and it is easy for someone (not myself, of course!) to become disoriented in the dark and fall sideway or forward into the telescope. You can see an example of what these ladders look like here.

They are just expensive enough that I find myself wondering where I might be able to find one used. I suspect that after 15 years of use, these are still fully functional, but sufficiently beat and ugly that I might get a deal on one--if I knew where.