I eventually found the purchase information on the web site, but I refuse to admit how long it took me. Afterwards, I received the following instructions:
www.x9.org Click on "X9 standards information"
Click on "standards store"
Click again on "standards store" in blue in the 2nd paragraph
Brings you to the ANSI ESS
Scroll down almost all the way and X9.100-140 is there.
P.S. It's $90.