If it’s just the weld I think the best thing is to have a welder weld it again. Probably be good for another 20 years.
If the tank is corroded, get a replacement VW tank from one of the several fine VW stuff venders–Cip1, Mid American, etc.
I’ve been looking at
these aluminum tanks but only with the idea of doing major mods–I want maybe to lower mine into the right side of the front pan so as to gain some “trunk space”–but I need a real small one to make it fit.
I don’t think any of these would easily fit where the stock one goes now; you’d be buying yourself a headache, imho.