Mouse rest arm for attaching to chair arm

I've been looking for an extension arm which can be placed on the arm of an office chair in order to use the mouse whilst sitting in the chair, but not close to the desk.

I've found these two;

The ErgoNav mouse tray
http://www.thehumansolution.com/ergonav.html

The MouseArm
http://www.mousearm.com/product.htm

These two appear to be good as they offer flexibility. I noticed a similar arm which has no flexibility and is quite rigid. Apparently the flexibility in the mouse arm is better for the wrist.

Just wondered if anyone knows of any other similar brands of this type of product as this is all I've been able to find. There don't appear to be too many on the market.

Or if anyone here has used these extension arms, I'd be interested to hear what you thought of them.

Thanks