title_body: Where should I look for food-grade nitrogen fills?
upvoted_answer: I talked to homebrewing supply stores looking for "Guinness mix" or "beer gas" pre-filled bottles for sale. While this isn't a pure 100% mix, it's about 75/25 or 70/30 and usually means the supplier mixed it for them. After a lot of digging at homebrew suppliers, I found that one of their suppliers does smaller batch orders, which can be difficult since fequently breweries sign up for a delivery schedule with large gas suppliers.
  
  The gas supplier is an industrial welding and gas supply store -- don't let "industrial" in the name dissuade you from calling and asking about food/medical grade. This industrial supplier also has food grade tank exchange.