Looking for a Plugin which I searched on google for more 10 hours but not found

Hello Everyone.

I have a special need. I did a long time google but no perfect solution.
I am looking for a Plugin enable to automatically insert certain html into post by category.
That means, I can pre-define a html content and relate it with one category.
Then if I publish a new post by selecting this category, those html will be automatically insert into post.
A idea example, I have two categories, flight and train.
If I post a article with flight category, I need to insert “Welcome my airport ” on every post head or bottom.
If I post a article with train category, I need to insert “Welcome my Railway station” on every post head or bottom.

I need such a plugin which can do this automactically.

I am looking forward to your answers!
Thanks in advance!