This is an openscad wrapper around estop_button.stl from http://www.thingiverse.com/thing:1805435, which allows custom text. Thingiverse's customizer doesn't seem to understand importing an stl file, so to use this, you'll have to download this scad file and the original estop_button.stl file. Open this scad file in OpenSCAD, edit the variables at the top of the file to adjust the text and size, then render and export your desired STL file.