Your Magic Mouse doesn't need a pad, nor will a pad make any different in how the mouse operates (unless your desk is a mirror). If you're just going to get one as a desk decoration, that's very subjective and it would be hard for us to recommend one. But hey, I'm a pilot, so try this one:
Airplane Cockpit / Aircraft Cockpit Cloth Cover Rectangle Mouse Pad 9.84"x7.87"
www.amazon.com