Tried La Concha. Bumped hard against a language barrier, but my fractured Spanish assured me that they only have pan de muerto. Called Carniceria Guanajuato. They might get some pre-fab skulls in, but weren't sure.
I'm looking for Dia de los Muertos goodies OTHER THAN pan de muerto. Made on-site. Legit. Would prefer to not have to walk through someone's living room to get to it (ie not home-made).