Most on the East Coast are small private family feedlots- feeding their own cattle.
Not much advertising done.
I know of one in Michigan that custom feeds(its the one I do business with) and I'm sure there are others but I have no idea how to find them other than word of mouth.
You could try contacting State Beef Extension agents and asking them.
If you find a list I'd like to see it too out of curiosity.
