Or maybe allow "size large" since that is more idiomatic for English.
I absolutely agree. I reported my answer:
"Do you have a size large?"
Which English (geographically), please?
I can say that definitely here in the US I/we would say it either way depending on the situation.
why is bigger not also correct? this seems like a more natural form in english
Большой is not comparative. "Big" or "large" is fine. "Bigger" is not.
Agree, the sentence is awkward in English, should say "a size large"
Why is "a large size" valid while "the large size" is not? What if the item comes only in Small, Medium, Large? (Which is very common in the US)
"a larger size" is not accepted.
"larger" is wrong. For "larger size":
У вас есть размер побольше?
I wrote the correct answer and it quoted it wrong!!!