Citric Acid

[yellowsocks.livejournal.com]

Sorry for a repeat question here - I couldn't find the previous answers for this in the FAQ, but where do I buy citric acid?

I can't order offline because I don't have a credit card and because I need it now.
I've read that you can buy it at a pharmacy but I don't really know where to look exactly.
Is it something I can pick up at Michaels, or Walmart?

Edited to note:
Thanks for the help everyone. I found out that Nutter's Bulk and Natural Foods carried 1 or 2 kg bags of citric acid. For those of you unfamiliar with Nutter's, I'm pretty sure its only found in Canada in AB, SK, MB, and NB. I don't really consider it a health store although it does sell herbs, and such, but to me it's all about the bulk candy. I was thinking this afternoon about whether I should scratch the bath bomb idea or fork out the money to order from the states, when I remebered that Nutter's was where I had bought all my epsom salts and sea salt the first time I decided to make bath salts. So I phoned them up and found my citric acid!

Thanks again for all the suggestions!