How do I get my commander to sign my N426?

Use the open door policy. Explain the situation, to include dates of when submitted. Be respectful, have tact and above all do not go in and point fingers.

Couple questions...Who did you submit it to? Do you know if it has made it to the O6? Do you meet the time requirements?

If you submitted this form 7 months ago, it hadn't even been a year since you enlisted.

Though it is typical to take a few months to move from CO/BN to BDE, it should not take 7+ months.

§1439. Naturalization through service in the armed forces
(a) Requirements
A person who has served honorably at any time in the armed forces of the United States for a period or periods aggregating one year, and, who, if separated from such service, was never separated except under honorable conditions, may be naturalized without having resided, continuously immediately preceding the date of filing such person's application, in the United States for at least five years, and in the State or district of the Service in the United States in which the application for naturalization is filed for at least three months, and without having been physically present in the United States for any specified period, if such application is filed while the applicant is still in the service or within six months after the termination of such service.