Monitor Arms

Hi I need to know a manufacturer of monitor arms similar to the Viewmaster 501 to take an IMac 24 " monitor weighing in at 11.5kg. I propose to attach to a custom made arm to which is attached the viewmaster arm or similar to give a range of positions to allow the monitor to be viewed from a wide range of bed positions, (to suit a tetraplegic ) hence the double pivot. The Viewmaster is on its limit for the weight of the screen so a little extra capacity would be helpful but in all other respects perfect. The arm I am looking at is at;
http://www.azlek.com/productdetail.asp?id=68&i=249 with the arm and one extension. Any information would be helpful