If you have some resources on hand for creating a reflector of some sort, you can go with a butterfly using the strobe and the reflector. Pretty much any basic white board of some sort will do the trick assuming you can get the light high on the subject. DIY Photography has a pretty good article on the technique showing a diagram and some outcomes as well as Jay has one here with much prettier diagrams. :)
Now, if you can't take the strobe off the camera but you can tilt/rotate it, then you can try to make it a bigger light source. One approach to this, again with the makeshift reflector is to direct the light to the side and onto the reflector that is then aimed at the subject. This will soften the light and make it bigger, creating softer shadows. A second reflector may be useful, if you can, to fill in the other side, further reducing and softening the shadows.
As a side note, the reflectors can be bristol board or something along that line, they do not have to be expensive, professional, options.