second source manufacturing is a inevitable outcome of open source hardware, people only buy "genuine" hardware out of a wish to support the developer.
Now, suppose you use the non commercial licence, do you think the Chinese sellers that make fake i-phones by day will give a damn? Using an incompatible non FSF approved license like that will only impede legitimate derivative makers, whilst the "cloners" will churn out cheap copies regardless.
Most hardware manufacturers will just manufacture your designs, they don't sell products to the public because that isn't their business, they aren't set up for the marketing and distribution for that. So I doubt you will have any problems in your "negotiations".