The official list of jōyō kanji 常用漢字 contains simplification information (e.g. 悪（惡） means "悪, which is the shinjitai of 惡").
The list of jinmeiyō kanji (PDF) 人名用漢字 also contains some info about simplification, in the opposite format, because here the meaning is "you can use 惡, which is the kyūjitai of 悪, in names."
These are probably the closest to an official list as you are going to get, if by "official" you mean "formally codified by the government of Japan." There may be websites who have rearranged the information so that it is in the sort of 旧字体:新字体 list you are after, but if they're privately run sites then they're one step away from officialdom.