This is a fully-parametric cane handle. It can be adjusted to accommodate any shaft size (circular or oval). The thickness and length of the handle are adjustable. The shape of the handle is specified by any mathematical function you like (by default: sine).

The .stl file here is merely a sample output -- it's perfectly sized to fit a stick I found in the woods. You'll need to generate your own .stl file from the .scad file to fit your stick.