Most Fats used Dupont Imron paints, still available from your local paint supplier. Touch up paint will usually be mixed for you without activator, so the paint will take some time to dry once applied.
I would suggest taking your frame with you to match, as Fat City always made up catchy names for the colors rather than using Duponts labeling.
We should probably start a database of paint codes...Fat City color, Dupont Name, RAL #
cheers,
rody