The breast growth spell is learned after taking Bell to the succubus tower. No idea where to get the cock growth spell, but I suspect it's from a similar situation?
to get it, you have to do Rinny's questline, in which you have to go through the graveyard and do a lot of stuff. (If you want to find more about tje quest, scroll down into other comments.) After the quest, talk to rinny about learning magic and she should give it to you if you have already unlocked the "Drain kiss" and the electrocution spell.