Not everybody has the either the time, skills, materials or tools to do that. Plus the first question was" Does anybody make a kit" not "How do I manufacture tubs"
If your putting it in your gonna have basic tools including a welder. If you have the skills to install them, you have the skills to form that metal. In fact, even if you buy them, your still gonna have to tweak them to the application, just like any other piece of metal you buy after market.
If someone feels that they lack those skills, then I guess it's time to pay up. I've got some ocean front property in kansas, you interested?