you know, finding the paint is the easier of the two task. The tough one is removing the old cresote and pitch. You have to do this to create a surface that the paint will stick to. I have a wood burning fireplace and in the off seasons I just spray it with cheap black spray paint, but your situation is completely different.
Go to a fireplace specality store and entertain this question to them.
What we use on our gas outdoor cookers will work, but getting off the grunge is the kicker. There is a high temp black paint for cookers readily avail at home centers.