I didn't have a committee letter from either my undergrad institution or my post-bac institution, and below is the letter I received from them. The Dean's Office at my undergrad knew exactly what kind of letter they were looking for, and it took them only a week to take care of it.
Thank you for your application to the Albert Einstein College of Medicine.
As you may know, post-bac applicants whose programs do not provide a statement about undergraduate good standing, must request a letter from the Dean of Students or Registrar at their undergraduate college affirming good standing status. Please check with your advisor at your post-bac program to make sure that such a statement was included in your letter. If not, kindly have a letter from your undergraduate college sent to the AMCAS letter writer service (Please see:
http://www.aamc.org/students/amcas/faq/amcasletters.htm). AMCAS accepts additional letters for Einstein up until February 15.
Please let me know when this letter has been uploaded to AMCAS, So I can complete you.
We look forward to receiving your completed application.