Born to us missionary in mysore India in 1942... need birth cert. asap?

Answer 1

Are you asking about proof of birth as a US citizen? If so, you apply through the State Department, this way:
http://www.travel.state.gov/family/family_issues/birth/birth_593.html
about halfway down the page, where you'll find "OBTAINING COPIES OF THE FS-240, DS-1350, AND PANAMA CANAL ZONE BIRTH CERTIFICATES"

Answer 2

In 1942?? Thats even before Indian Independence in 1947 and when the Brits were still there. Do you have any contacts in India? If yes, you have to produce an affidavit saying that the DOB was not registered but you need some one to sign the affidavit saying that you were born on that day, in mysore. Its about a 2 or 3 month process and can cost you soem money under the table to get out of the Indian redtape.

Talk to someone who is in mysore or atleast Karnataka already. That will help you a lot.