If the grocery store you go to sells short ribs that are trimmed up like the ones in the picture below, they have the big dino bones in the back. Just ask the meat guy/gal if they have any of the beef short ribs that aren't cut up in the back. They will normally have them in cryovac packs in the back. They will bring them out, and you can either buy the whole cryovac (which I do) or you can ask for however many bones you want from them and they will portion it out and put it in a chub and slap the price tag on it.
The beef short ribs are between the fatties.
The big thing with shopping at grocery chains is that they have a standard procedure on how they do things. Don't be afraid to ask them if they have a certain cut of meat, or have the meat before it is trimmed up. They are always more than willing to help you out. If you go to an actual butcher, be demanding (but not a pain in the arse) Ask for the specific cuts of meat you are looking for. Look at the meats with the best marbling etc. Ask questions of where the meat was raised and what they were fed. True butchers will be able to answer your questions and will appreciate the fact that you are looking for quality meats.
Whenever I go to the two butchers in my area they know that I am looking for a quality piece of meat and when I ask them for what they have that is good, they will recommend something. It sometimes it is the most expensive cut of meat, but normally it is a well priced cut that has fantastic color and marbling.
The meat department at the 4 grocery stores by my house, all know me as well since I'm typically asking for certain cuts. 3 of them will cut the spare ribs in half or 1/4 racks and sell them by the chubs, they will cut down the pork butts to smaller pieces etc. I am the guy that is always bugging them for the big hunk of meat or uncut ribs.