As far as I know, there are no more Atwood 6-gallon tanks to be purchased new. Dometic bought the Atwood water heater line, then discontinued it, in favor of their Dometic line. The last new tank for sale was sold over a year ago.
Your choices are:
1) Find a welder to repair the tank and guarantee the repair.
2) Install a Dometic six-gallon water heater. Unhappily, it is a different size and shape (higher and narrower, so you need to enlarge the opening and replace the door).
3) Install a Suburban "Direct Fit" water heater (link here
). Suburban saw an opportunity to sell water heaters to orphaned Atwood heater owners. They claim the "Direct Fit" is a drop-in replacement for the six-gallon Atwood.
4) Install some other non-Dometic water heater.
5) Buy a used, working six-gallon Atwood.
If you go with the Suburban "Direct Fit":
1) The tank is porcelain-lined steel, so you'll have to deal with an anode rod from now on.
2) The SAW6D appears to be propane-only, while the SAW6DEL appears to be propane/electric. You should confirm this for yourself.
3) You may need to buy a new door and a new interior switch.
Let us know which way you go.