Couldn't find the kind of sign I was looking for so I made one. Starting with an SVG file from the web of the standard restroom icons of a man/woman, I then used DNewman's excellent Inkscape to OpenSCAD plugin to export the image to an STL (toilet-figures.stl). I've included the SCAD output as well. Then using Tinkercad.com, I put the figures on top of a rectangle to approximate the sign I was looking for. I've included both an outline version and a stacked 'extruded' version depending on how you'd like to print them. The outline version is pretty straightforward. The extruded version can be printed in two colors by pausing the print at the 4mm mark and swapping colors (I have a single extruder MakerBot Replicator 2). Tinker the extruded version or the outline version on Tinkercad.com