Have you tryed googling it? You can also try etsy.com or ebay. Pattern Review often has out of print patterns, too.

Here's the link for Simplicity They offer "out of print" patterns on their web site, too.
http://www.simplicity.com/c-164-costumes.aspx?pagesize=99999999
You might also want to try the following http://butterick.mccall.com/religious-pages-874.php

I hope this helps.n *'s

Do you know the pattern number ??

The pattern companies will sometimes have them is stock if you call them. Especially if the pattern is not listed on their site. I have gotten quite a few older patterns that way. --Judi

Maybe you could find it on ebay????

Using any button front shirt pattern that includes instructions for a band collar in addition to a conventional shirt collar these instructions on this web site will guide you to making a clergy shirt.