Interesting question, Chris.
First off, flank steak has gotten hard to find under any name. It's not as popular as it once was, for various reasons, not the least of which is price. I've seen it at almost eight bucks a pound, for instance. That takes it out of the relm of "inexpensive cuts."
Even so, if you search you may be able to find it. Try asking at the butcher counter.
I have seen it occasionally mis-identified as London Broil---which is a different cut. The flank is much thinner. And the local Kroger sometimes puts it out as "marinating steak," which is a term I never heard until about two years ago.
We love flank steak, ourselves, and are always disappointed when we can't find it. Or when it's so expensive we may as well buy a top cut and be done.
Good luck with your search.