I have not looked for this product in probably 10 years, but I expect that it is still available. The product is found in the area of the auto supply where the sealants such as RTV and gasket sealers are located. It is a dough that you simply press around on the hole in the gas tank. You must first lower the gasoline level below the leak.

I put this on the very bottom of the gas tank on my ranch truck about 10 years ago and it is still holding. A very good product.

Good luck,