Actually any hood not getting in the lens field of view would do the job properly (but for hoods designed for wides, pretty useless on a 50mm).
As for generic Chinese hoods (sold by Heavystar or another seller, they're all the same stuff) the recent tilted & vented hoods (copies of the Leitz 12585 one) are way better made than the cylindric first series (they're now machined from one lone piece of aluminum, not tapered any longer) and a bit more efficient in terms of actual lens shading.
The original Zeiss hoods for the Sonnars (either prewar or postwar, were they crackled black paint over brass, bakelite or aluminum finish) aren't too difficult to locate but they get so much into the camera viewfinder that rather not using them in the field.