Does it have to be anhydrous? Seems like a waste to go for the more expensive stuff when you're going to dissolve it anyway. Food-grade citric acid monohydrate should be cheaper.
The manual just said a citric acid solution so I guess whatever source will do. I suppose it’s just as easy to get a reasonably accurate concentration if you account for the water already present in monohydrate.
According to another comment - you're _not_ missing the printed ink on your dishes. If you are happy with the state that your dishes come out of the wash, then you are fine.