If you are cooking the food or feeding raw, you can buy the meat at any grocery store. I have no clue how to feed a cooked dog food diet but there is not need for a special supplier. I would assume a cooked diet is mostly the same with lots of meat but they probably add in grains, veggies, and lots of supplements. I have seen cooked recipes before online and it looked way too involved (so much grinding!) and time consuming for my personal tastes.
I buy chicken and liver mostly from Save-a-lot, Aldi and Wegmans, depending who has what on sale. This week Save-a-alot had whole chickens for .79/lb. I usually get quarters for .49 on sale too. I can get pork roasts for a good price at all 3 stores too (sometimes .99 for bone-in and 1.69~ for boneless).
I get turkey, pork hearts, beef hearts, liver and kidney from a local Polish meat market that sells all kinds of meat, packaged goods, produce, etc. If I call ahead I can get a better price by asking to order a case vs just coming in and buying 10lb or whatever like normal people do. We used to have a great restaurant supply place with cash/carry but they closed.
I am also lucky to have family members who hunt and give me venison and I do run a CL ad in the summer/fall before the new season starts. I was lucky this year to get about 80lbs of free venison from 2015-2016 seasons off of local people.
What I am getting at, is that you can buy whatever you need for a raw diet in human-food stores without having to go out of your way to find some kind of dog-meat supplier.
If you were interested in raw, the facebook group "raw feeding (rf)" is a good place for the simplest version of raw feeding. The group is a bit militant on what can be advised or said, it can induce some heavy eye rolling, but they offer pretty straight forward information for getting started/troubleshooting.