Joystick Math
Some explanation about +Y to +Y and -Y to +Y outputs:
This splitting allows two functions control by one axis, one for positive joystick movement and second for negative movement, on both outputs from 0V to positive voltage.
This can be used for any input voltage (for example splitting sine to two outputs=two half-waves, both outputs positive)
http://www.youtube.com/watch?v=s3kufpc7RUU
No info about availability.
$65