Rendering a "point" (pixel) in blender

Hey guys
I’m wondering if there is any way to make Blender render constant-in-pixel-size marker in space. For example when camera is rotating 360’ around some character I would like to have 1 pixel red(or blue or whatever) overlayed in place of each eye. Even better if it can be done in previev somehow.

Does anybody know the way to do that? It will save me a tons of work (placing like 4K points by hand).

Thanks in advance.