True tanks are not available new but that's not to say their not repairable as good as new?, repaired one today with no less than 10 holes!
But, this leak could be very simple, the bolts holding the element are prone to corrode and lose their heads, literally!, this releases the pressure and allow the water to leak from the elements seal, a simple gas/electric reseal kit sorts this out.
Beyond that, 99% of the leaks I'm fixing at the moment are purely down to frost damage, ie, the tanks been left with some water in and it has frozen, the expansion of the water freezing has then shoved the tank back off it's seal to the heat exchanger.
Only cure here is to straighten the distorted tank or it will never reseal successfully, and again a new seal kit and possibly a new tie rod completes the job.
I can help with any part or undertake all of these tasks