Lebkuchen in Frankfurt?

Hello,
provided they exist, does anyone have lebkuchen stores to suggest in the center of Frankfurt? Given that next week I'll have a 4-hour plane connection stop at Frankfurt airport, I was considering having a quick walk around the center and perhaps bring home some lebkuchen, as they can't be found in Milano. If anyone has a clue on where I should head to, thanks!

Cheers,
Andrea