Manual focus viewfinder accessories?

[PaulWog]

Are there any accessories that aren't too large that I could add to my D5200 to improve manual focus when using the viewfinder? I have 20/20 vision, but my viewfinder as it is just doesn't cut it. It's a pain to look through, and hard to bring up to my face correctly. When I do have it up to my face, I find I can't tell closely enough where the center focal area plane is.