TrackPoint a.k.a pointing stick 2-axis force sensor
I'm collecting info about the history of trackpoint to avoid re-inventing wheels (and put into web resource).  It appears that some mil-spec and industrial applications have put the tech to use, here's a group that may be available;
http://www.ultra-msi.com/miniature-joystick-models.html#force.  I may have useful info for you in future.  I've worked with strain gauges and MAY reconstruct the crime (after understanding the patent trail better).