Looking at period photographs, there is a difference between MG42 cocking handles. One seems vertical, one seems horizontal. The horizontal ones are seen earlier in the war, and the vertical ones rarely on late examples. Where these discontinued after a certain date to be replaced? Where can I buy one?
Oooh! Collectors everywhere want one of them!! Rare and therefore expensive as only the 'pre-adoption' MG42s had them. The MG42 was officially adopted in October 1943, by which time just over 17,000 had been made in 1942, and total 1943 production was around 119,500, out of a wartime total of some 400,000. I can't establish exactly when the changeover occurred to the upright cocking handle, but clearly several thousand were probably made! Being early examples they are less likely to have survived though...
It is much harder to cock the weapon with the slab-sided handle, and there were many complaints from the troops, hence the change. Waffenmeisters were also authorised to retrofit the new style handle or fabricate an adapter which gave a bit of extra leverage.
Good luck in your search, they are like hen's teeth on their own. One occasionally sees an original 1942 dated MG42 for sale with this handle, but at a considerable premium!