I always called them axle stops, but they might have had another name. I have no idea whether anyone is still making them so your best bet might to ask in the C&V forum.

They are used on both sides (or on some bikes only on the left) to set stops so the rear wheel can be quickly returned to the same place in the dropouts thereby eliminating the need to center each time. Over the years this design gave way to the micro-adjust screws which served the same purpose until vertical dropouts became the norm.

BTW- they aren't necessary, just convenient