grammaticality - "Are those a new [object]?"

First, a basic grammatical point. Copular verbs like be don't have objects. The words that follow them form the complement or, more precisely, the subject predicative.

The normal patterns are, to continue the interrogative construcion:

Is that a new hat?

and

Are those new shoes?

However, it is just about possible to imagine a native speaker saying:

Are those a new pair of glasses?

Here the plural form of glasses overrides the singular form of a new pair.