I'm afraid I don't have all letters in the previous artwork. I probably still have my old font folder backed up somewhere (unfortunately well organized backups of all files are not my strong suit), and could just reinstall the bunch of fonts I'm still missing. I just feel GIMP ought to be able to tell which font it still needs. I mean, clearly the info is somewhere available to the program or it couldn't match the name to the font if it is installed.