Haven't seen it, but heard it's a tiny pinhole leaking gas. Is there a non-welding solution that will work, or is it destined for the torch. I don't know of anyone around my neck of the woods with balls enough to do it.
I got some putty in a tube at my local independant auto parts store. It was labeled as gas tank sealer. It looks just like plumber's putty, or some version of JB Weld. It's two-part stuff with the reactant in the middle. You know, slice off a chunk and knead it with your fingers.
I had some nice holes at the lowest point in my BMW tank after I wire-brushed the rust off. I plugged it with that stuff and it held fuel for the five or so years I owned it. I sold it to a friend and it stayed fuel tight - at least until the bike dropped an exhaust valve and he sent it somewhere else to live.