One of the things I've found is that if you go to your local butcher, either the specialty shop or the chain market, talking to the guy behind the counter is worth the effort.
Lots of times they will give you a good price on a large boneless roast or shoulder that for "eye" appeal would have to be trimmed out. You want lean meat, but need a little marbling for flavor and to keep it from being to mealy tasting.
Tell them what you want it for and in my experience they will give you a good deal and even slice it into 1/4" slices and you can cut it from there into the size you want before marinating. Often they have cuts of meat close to expiration date and will discount heavily to get rid of them. For marinating and making jerky, its perfect.
We have Kroger's in my neck of the woods and there meat is excellent.  Buying a big piece of meat with the discount Kroger card can really give you some excellent jerky meat ;)