I did not pay an expediter. They wanted $600!
I paid the expedited fee and expedited shipping fee directly with my passport. I filled out the form online, printed it, and mailed it from a post office express mail. I followed the progress online. US Passport service also gave me email updates.
When you fill in the dates for travel you can put a much closer date than December.
From their site:
https://travel.state.gov/content/travel/en/passports/have-passport/renew.html
Processing Times
Routine: 8 to 11 weeks*
Expedited: Costs an extra $60. Takes 5 to 7 weeks.*
*Processing times begin the day we receive your application at a passport agency or center, not the day you mail your application or apply.
Expedited at Agency or Center: Must have international travel in the next 14 calendar days.