Hi All, I found a bulk, powdered, Vitamin C (Vitamin C Ascorbic Acid Powder). I will be switching to this from the tablets when the tablets are all gone. The bulk powder won't have the additives they use to make the tablets. Also, I can measure the amount I want to add easier.

This is a 5 pound container on Amazon for $27.91 on 6/4/2012. Shipping to me in North Carolina was only $2.49. Less than the cost of gas round trip to town.
NOW Foods Citric Acid Powder Bulk, 5 Pound Tub