they are relatively rare.
Go to http://www.cigarfamily.com/
find the Opus X page, then click on authorized retailers - this will let you find stores that carry them in your area. Then just start calling places to see if they have any.
If they don't, they usually get shipments of them 4 times a year.
Very limited production cigars. Very good but expect to pay a lot of money when they're available. The Fuentes have done a good job of marketing their products but with the way ISOMs are smoking now, I don't know if they're worth the price.
IIRC, if a store is an authorized dealer, they're only allowed to mark them up a certain percentage. Apprentely, Fuente doens't want price gouging. However, there's no authorized ones around me. The local B&M wants $23 for what they've got. That's why I've never smoked one yet.
I did find one online store that had them between $10-$20 I believe, but didn't state if they had any in stock or not. I emailed them, but never heard back!?!