We do not use the wood burning brick fireplace that came with our house. Because there is so much cold air coming down the chimney we would like to block it off from the inside. Is there an insert we can place below the damper so we can cut down on the draft? If so where could I purchase one. I've checked the local hardware stores here in southern NH.

It should have a built in damper, you can close off manuelly,, is the chimney used for anything else?, might be the easiest to climb on roof and close off from the top

Are you looking to install a gas fireplace insert, or just close of the chimney?