Dmitry,
Do an online search of "Oral Rehydration Salts." Many distributors sell them online.
Also, I just purchased them from Nancy Shura-Dervin, who is a member of this forum. The manufacturer is Jianas Bros. Packaging Co., Kansas City, Missouri:
www.rehydrate.org/resources/jianas.htmJianas Bros. require a minimum purchase of a carton which contains 125# packets at $0.55/ea. 1-4 cartons is $68.75 per carton.
If you don't want to purchase a full carton, which I didn't because I didn't know if I would like them, Nancy will sell any amount to you for $1/packet. It's the same formula of ingredients described here in this thread.
--TrailTrampler