None of the examples require an article. And, they all may use one.
"What size do you take, sir?" "A nine, please."
The article is nice, here. but still not required, as the question left no doubt the response would be a size.
Using the article is fine today.
I believe the use of articles in the examples would have been idiomatic 150 years ago, though. We have some literature on problems learning English by persons whose first language does not use articles, and, the difficulty in learning them. I have not been able to find any studies on Italian, German and Yiddish speakers, who knew articles but used them differently. However I have reason to think such a use as:
I take a size one
came from 19th century immigrants. It is not important that this be proven or not, but that :
I wear size 12
I wear a size 12
are both acceptable, and seem to indicate an innovation occurred at some point.
Note that it is still not common usage to use the article in some constructions:
I wear a size 12 shoes
I wear a size 4 dresses
I would not use the articles. But, as to the examples in the question, the use is optional.