The doors on the CLC are the same as the w203 coupe. Therefore the door mirror seats must be the same as a w203 saloon. Therefore the CLC arrow mirrors might fit a w203?
The W203's mirror is attached to the car (item 10 below), where as the CLC has a small stem to the mirror - looks ever so slightly smaller - 2-3cm smaller (I hope that makes sense)
Someone with a very upto-date EPC will be able to check the size of the mirror surrounds/connectors to see if this is correct for you.
That would be a nice clean mod, as i recall the wing mirror is slightly smaller than W203 as tried to order CF wing mirror covers for friends CLC, and they wont fit, but do fit W211.