I finally found a local source for citric acid. My local feed store has it in 410 gm (a little over 14 oz) packages. I got almost 6 pounds for $12 and some change. I also got a 50# bag of baking soda for $14, and they were able to get me a better price on muriatic acid than my local hardware store.
You guys might check your local feed store to see what they carry.
You guys might check your local feed store to see what they carry.