Here is one of our unique Canadian designed and made medical devices. It may be right for one of your clients. http://www.symmetric-designs.com/axion/

The Axion Rotary Interface    

A Unique Device that Permits Wheelchair Headrests to Rotate

The Axion Rotary Interface for Wheelchair Headrests can be attached to most headrests and hardware.  It allows headrests to freely rotate, improving the function of the user.  The Axion is applicable to those with limited head control, limited range of motion or field of vision.  It is also applicable to those who frequently rotate their head against a headrest.

The Axion is available in four versions, to fit two sizes of balls (1" (25mm) and 3/4" (19mm)) and two ranges of rotation.

• Axion 60 series permits a total rotation of 60 degrees
• Axion 90 series permits a total rotation of 90 degrees

Benefits

• The Axion Rotary Interface is quiet, free running and it does not require lubrication.  
• The range of rotation can be limited or stopped by means of a simple knob control.  This allows the headrest to be positioned at a fixed angle or be free running.  Some drag may be introduced to slow the rotation, if desired.

Usually the Axion will be used to allow free lateral rotation of the head with the headrest.  This  permits the head to be fully supported by the headrest as it rotates.  The benefit of this to those with muscle weakness is assured support from  the headrest as they rotate laterally. For those with good muscle tone but having a tendency to rub frequently against a headrest,  the Axion allows the headrest to move with their head.  This can reduce or eliminate the friction  between the head and the headrest, so reducing hair loss or abrasion of the head.