What should I do next, regarding an incommunicative employer who owes me agreed-upon money?

I wrote 4 articles for a hyperlocal NYC-based publication. I had a very nice working relationship with my boss, whom lived nearby. He told me that I could bill him whenever I like, either after the articles were published or as they accumulate.

In recent months I had graduated and moved out of the area, but still was planning to write for the publication, which he acknowledged and was all about. During that time I still wrote him (my boss) pitches, and even attended a launch party for the print version release of their publication. I also sent him a bio to add to the website as an official contributing writer, which he never posted.

The second paragraph details aside—he owes me money. I’ve sent emails with correspondence and an invoice. I called him phone today and I believe I was sent to voicemail.

I don’t know what to do. I am trying not to take this personally, and chalking it up to the fact that he is busy. But he is incommunicato, and I am pissed off. They money isn’t overwhelming, but it’s money nonetheless.

I have another email for his wife, who he runs the publications with, but with whom I have little relationship.

What do you think I should do? Email his wife/business partner too? Track him down somehow?