Lucas Transmission treatment is the one product they have that I have heard from friends and online commentary that actually works fairly well, but not so much as a stop leak. It's not the first thing I would use to try and revive a problematic unit, but maybe more as a last resort.
I have used Auto-Rx to clean and revive older units, but not necessarily to stop leaks.
I used a quart of Prestone brand transmission stop-leak that I found at WM and it worked well. This was a quick fix for a car that no one was keeping the fluid levels topped off regularly and it was nearly running out of fluid between times when I would get to it. It slowed the leak down to a trace, and the thing I liked about the Prestone brand stuff was that it looked, smelled, and poured like a fully formulated ATF rather than a strait dose of solvent like some of the others. The FWD Chrysler Cirrus that i used it in was not leaking at the pan, but rather the seal behind the torque converter. Now when I check the fluid level, it is usually not down much more that half a quart.