We can use 才貌双全 to describe a person with both 貌 and 才 and 德才兼备 to describe a person with both 才 and 德.
Does there exist a 成语 that describes a person with all of the three?
We can use 才貌双全 to describe a person with both 貌 and 才 and 德才兼备 to describe a person with both 才 and 德.
Does there exist a 成语 that describes a person with all of the three?
No, I don't think there is an idiom describing all of the three.
In Chinese, it is very common to use parallelisms, such as "他才貌兼具,德艺双馨". I used little different terms from yours and parallelize them together to avoid literal duplication.
As a chinesse girl, if we meet a man with three of those at this time, we call him as 男神(just like 女神goddes,who are perfect).
there is 才貌耀德 you can use it in writing, but don't use in oral Chinese.