(1) Permatex 3J (or 3H or 3D, same stuff just different size containers)
(2) RectorSeal No. 7
(3) Seal-All (made by the same people who make Goop)
The RectorSeal No. 7 is a plumber's putty that is pretty expensive, more than $30 for sure. I'd try anything and everything before this.
I'd go to your local auto parts store and read the differences between the Permatex and Seal-All. I have used the Seal-All and it didn't work for my purposes as I was trying to seal two pieces of my plastic gas tank together... and apparently, that's the only thing that Seal-All doesn't work too great on -- shiny plastics. It'd prolly work for your situation a lot better than mine because I was trying to secure the mount to the gas tank, which means the Seal-All suffered from heavy vibrations and extra pressure as this hole was near the bottom of the tank. I filled it to the top, and it didn't leak for a couple hours, then slowly it started dripping a drop at a time... then the next day, my tank was nearly empty.
Go to the hardware store and get a spring clamp. Look in the area woth the little drawers where there is all kinds of miscellaneous hardware bits. I mean a real hardware stor, Ace, etc., not Home Depot or Lowes.
Personal opinion here, but sealants and adhesives are not the way to go here. they have their place, but if you have fueal leaks, you just need the right sized tubing and a proper clamp.