We have a ceiling fan that was in what used to be a dining room, but is now a studio and we removed the light. We need to find a cover plate for the electrical, but have not had any luck thus far. 3" in diameter and has two holes.

Home Depot and Lowe's carry them, I just installed one a couple of days ago. 3" is an old box and you will need to use a cross bar. Here is an example.
Flat White Ceiling Blank-up Canopy for Raised Ring or 3-1/2" Box (http://www.garvinindustries.com/electrical-box-covers/4-round-octagon-box-covers/white-ceiling-blank-up-canopies/cbc-f)

Thanks but need to add a picture to better describe issue. Not quite what I was getting at.

Not sure what ceiling box you have. As I noted, older 50's vintage houses had 3" boxes. Give us a better explanation.

Are your referring to the box that is below the fan where you removed the light and not the ceiling box?

Exactly... I have been trying to add a picture but cannot figure out how.

If you look below the box you are typing in you will see an "Go Advanced" button, click that and you will be taken to a screen that lets you post your pictures.

OK, now that is clearer. I'd just cut and tape a piece of white poster board over the hole. The part you are looking for may be brand specific and hard to find.