You can purchase the Extension Arm for this Maxita Stitching Clamp here.
 
The Maxita Adjustable Stitching Clamp is designed around the simple idea that tools should adapt to the maker, not the other way around.
When stitching, the height, working distance, and angle can all be adjusted to suit your posture, habits, and project, allowing you to work comfortably whether seated or standing.
The clamp can be secured in different ways to suit various bench setups.
Thoughtful details include a built-in magnet for safely holding needles when you pause stitching, a cork slot for keeping your awl close at hand, and a discreet hidden closure that prevents thread from catching during use.