Years ago a radiator shop was the go to place to repair tanks. They were experts with silver solder and could pressure test the tanks to be sure there wasn't any other leaks you might have missed. These days, finding a radiator shop that actually does something is getting pretty hard. There are none within 40 miles of my house. If you have one nearby, get a quote on patching your tank and go from there.

I'm also not a big fan of gas tank coatings (inside or outside), I've seen and heard way too many horror stories.