Your best bet would be to find a used replacement from a junk yard. Where are you located ?
Do you have specific truck salvage yards, like Pick and Pull in your area ?
How big is the hole ? Is it round or a straight crack type ?
If its round, you can drill through,(use a smaller tapper size drill than what it is called for, because its plastic), then run a machine tap through the hole, then put a machine screw in the threaded hole. If I were going to do that, I would find a VERY thin O ring to put behind the head of the screw, for the actual sealing material.
When that's all complete, clean REAL good with lacquer thinner, THEN put some 2 part epoxy on the head of the screw, and overlap onto the surface of the fuel tank.
If you go that route, check on it every once in a while just to make sure it has not vibrated loose.
Damn I hate plastic !