Step one...
Try tightening the screws that go thru the tank and the gaskets may seal up and be fine. You can't get the gaskets from Whirpool, but I have often seen them on Ebay so you should be able to find some new ones to tide you over for the next 50 yrs.
There are two gaskets. One goes on the underside of the tank and one on the inside of the tank.