You need a premium market or a butcher's shop.
Her in AZ the only "supermarket" in which to get it semi-consistently is AJ's, the premium branch of Bashas' (sic).
Where to buy USDA Prime 1474
tuppy Not necessarily. I've had live lobster Same Day delivered, packed in a special container cooled with dry ice but in such a way that the...
N.B.: USDA Prime is not cheap, typically 2-3x the price of choice, and it's not guaranteed to be better than choice. The entire carcbutt is graded, and the grader can't see into the particular cut of meat you're buying, just the exposed edge of the slit cut into the side of beef that he's grading. So, fairly often, you'll find cuts from Choice-graded carcbuttes that have all the marbling of nominal Prime beef. And, sometimes, it goes the other way, and the Prime looks almost like Select. The grades are based entirely on eyeballed fat percentage have correlation with the quality of the lean meat or the aging.
Your eye on the cut you're asking them to wrap up is the guide.
That said, one of the best steaks I ever ate was a 16-oz Prime strip that I got at AJ's ($18-lb, iirc) and seared on my home grill to leave a cool center with the marbling still visible. I still close my eyes thinking about that one.