NEITHER + SINGLUAR NOUN Here "neither" means "not one and not the other", and the verb is singular: e.g., I must see my friend on Monday or Tuesday, however, based on my busy schedule, neither day is available. NEITHER OF + PLURAL (noun or pronoun) In a formal phrase or sentence we use a singular verb. e.g., Neither of the governments is willing to take the first step. In an informal phrase or sentence we use a plural verb. e.g., Neither of us are going to the party.

Both are commonly used. "Are" sounds better to my ear as a native speaker, but "is" makes logical sense.and probably is grammatically correct.