Let's be honest they do not make them in the original way with large heavy duty presses etc. They make them by hand like a cottage industry so I guess that some will fail the quality test. However as nobody is ever liable to commit to the huge capital investment in the western world in order to tool up production. then your choices are extremely limited. Buy from India, repair your existing tank or try and find a high, quality old tank. To establish the scale of the problem just look at the many hundreds of different tanks made for the hundreds of different models and variations from the huge number of manufacturers. All to be made without the detailed drawings of the originals.