The best replacement for stairs is steps.

The best alternatives to stairs are rated as following:
★★★★★  steps
★★★★★  elevator
★★★  escalator
★★★  running
★★  ramps
★★  escalators
★  ramp
★  elevators
★  squats
★  hill sprints
★  hills
★  ladder
★  stair
★  carpet
  downstairs
  lunges
  waterfall
  spiral staircase
  climbing
  spiral
  ladders
  stairmaster
  oak stairs
  staircases

Your alternative for stairs is not listed? Suggest!
Speaking about stairs, one probably shouldn't forget about crutches.

Other search terms related to stairs and their ratings are:
★★★★★ crutches
★★★★★ risers
★ hardwood
★ ramp
★ white risers
painted risers
You have in mind a companion for stairs and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of stairs in all years. Click on graph for more.
stairs
steps
elevator