Rotten tank - solution found

They don't know about the niche market. There will only be a few dozen -
perhaps more, customers - but once the mould is made a batch can be run
off at any time in the future.
A lot of fibreglass work is like that - small lots in batches.

 

Got a leaking but a tank but still retaining its' shape.
Then no problem making a two part mould seamed around the base.
Make it out of glass fibre.

You could even apply a coloured gel coat and knock them out one every
other day, if you wanted three layer build. Glass or carbon fibre.

And in glass fibre they would be cheap to make and not beyond DIY

BUT

Getting the necessary ticket to say they can contain petrol would be a
problem, if you wanted to sell them.

 

"Show use only"

 

!!DING!!

With a donor tank for fittings it should be easy.