Let`s assume you have a product, design, and the money. One place that seems to be pretty comprehensive would be Thomas.net
Another option you might consider would be to start as a craftsman, where you create one-of-a-kind pieces, using steel you buy via retail. It might not be a great way to have a "big" business, but I`d argue that it would help you with market research.
If you were to make 1 single item, regardless of costs, then go about selling it, you`d get a strong sense of what`s involved. That would help you understand each of the other steps you`d need to understand. Sort of "intelligence bootstrapping." :-)