I've used JB Weld before, the results were pretty good, so does Super Glue, which I used once to cement a fuel line in place on a Homelie BX90 power blower, it worked well up until I took the fuel lines out again. There really isnt a large list of things that will hold up under gasoline.
If the two things I menioned dont work, try one from the other members here. Something is bound to work.
I have used a plastic tank repair kit from an epoxy company with excellent results. Actually put a broken piece back in and it has lasted over 2 years.
The secret is to clean the tank, rough it up, and clean it again before repair. Most of the epoxies work just fine if you get a good bond.