HG,
I used the Eastwood tank sealer kit. It's pretty involved. Once you start the process, you have to finish it in the time prescibed in the instructions. It turns the inside of the tank into a porcelin shell. Pretty neat stuff. It will fill small pin holes like the ones shown in your photo.
I feel your pain. New tanks aren't cheap. One other option might be to take it to a tank repair shop and get a quote. It may be less expensive than the repair kits mentioned. You never know until you ask.
Tim