Only one local store, out of about 8 different stores/chains, sells pork fat, as such. Marked as "pork fat for seasoning" @ 49 cents a pound. But they also sell pork snoots, ears, upland "oysters", chicken feet and a variety of other exotic stuff found no where else in town. My favorite place.
As for the other stores, I've had mostly no luck. Either they don't butcher or trim locally, or they use the trimmings themselves to make brats and Italian, or simply tell me "we don't sell that".
Slab bacon would be an option, as would fresh side meat or fresh jowl. One store sells 5 pound boxes of "ends and pieces" of cured bacon......but that is mostly fat. What cure there is in it would likely not be noticeable in a sausage.