A medallion is a good solution.

I needed to use these on some of my Lightolier recessed lights. Check with your recessed lighting manufacturer for wide flange rings that fit your model lamp.

Here is a link that might be useful: Lightolier Wide flange

Modernhouse,

I want to make sure that I understand, the ring that you are refering to is similar to the ring that fits over the opening for the recessed light?

I am attempting to install a hanging pendant light in place of recessed light, thus the hole in the ceiling is larger than the normal sized outlet box hole. Will what you are refering to work for this? Thanks!

If you all are speaking of medallions as housesavvy suggests, there are several sizes and styles available at the big box stores.

Sorry,
I misunderstood that you needed this for a recessed light fixture. That was the mistake we had to cover up in my case. These trim rings do not apply in your case.

These are similar to what you mean. They're available in metal or Kydex. I believe you can have the kydex ones custom cut

Here is a link that might be useful: Oops Rings Escutcheons

Thanks pound. In the same situation: replaced 5" recessed bulbs with a pendants on a wire. Big ugly holes up there now.