See this previous discussion: (there was a url link here which no longer exists)
AFAIK there is no one who imports Fuji's equivalent product, Ag Guard, to the U.S., but perhaps that will happen now. Sistan doesn't seem that hard to make, either, so maybe one of the hobbyist suppliers will give it a shot.
I'm not that thrilled with Sistan - I've gotten too many prints with bleached spots where the stuff has dried in drops. Kodak Brown Toner seems both more effective and less harmful. If only it wasn't for the smell ....