I tripped it today. The part no is 126 505 06 55 and they seem to be commonly available new. It has a cut out on the lower driver side fan side. ( round) . BEHR. Need a dimension?

It is this: https://www.pelicanparts.com/More_Info/1265050655.htm?pn=126-505-06-55-INT

Says

For select models of 300TD, 300SD, 300D, 300CD these guys list many models for fit: https://www.ecstuning.com/b-genuine-mercedes-benz-parts/fan-shroud/1265050655/#tabDoesItFit