From what I could find, Emergen-C is a GREAT source of this. I used to drink it on a daily basis (check it out online--it contains no refined sugars), but I sort of tapered off. I'm going to buy it and add it to my daily regimen once again. It's affordable and comes in 36 pack boxes. Hmm..the cost ranges around the country, I'm sure, but here in CO, it runs anywhere from $7.99 - $11.00 a box. Thanks for the info!!