Any butcher worth his salt would order you in some prime upon request, even if it's not something he normally stocks.
The same goes for any random ass cut you saw on Iron Chef and think you just have to try.
As far as "choice" meat in supermarkets, yes, some carry it. Most meat you see in the market is actually a grade down though, "select." Particularly if you cant find a USDA grade sticker on it, it's most likely "select" grade. (as in, don't select this one)
Many market carry both, touting the choice cuts as some grand thing and proceed to charge prime prices (or nearly so).