You will find some staircases WITH handrails in the free model collection. And lots more in the other model sources, eg. 3d warehouse.

A closed handrail (no balusters), you can simulate with a sloping wall. But beyond that the geometry of a staircase and its rail can be pretty challenging. Architect and Biennale di Venezia boss Rem Koolhaas just quoted a saying that stairs are the "queen of architecture". But while conceiving a good staircase can be hard, drawing them with Blender/Sketchup/ArtofIllusion is relatively straightforward. See Models Import Page for more info on design tools and other sources.

But if you have a need for something very specific, I am afraid you need to give some more detail of your needs.

ok