We have the same dilemma, and came up with a satisfactory (for us, anyway) answer by using a diamond-plate toolbox from my old Ranger pickup. We store some of our gear (awning, swim gear, etc, nothing too heavy) in the box, which we load into the camper "doorway/hallway" when traveling. When camping, the toolbox is taken out to become a small step/porch/storage site for the camper with the addition of one or two single-step stools.
We looked at step-ladders and other ideas before re-purposing the toolbox which was just taking up space in my shop, anyway.