Do you need a finished product in hand to approach manufacturers about licensing? That depends. Lisle accepts inventions in most stages of development, from drawings to products that are already on the market. In fact, he actually prefers to get products that aren't yet on the market, since his engineers perform quality and cost engineering on all products prior to manufacturing.
Lisle is willing to accept unfinished products because he has the engineering resources to devote to perfecting each accepted idea. This isn't the case for manufacturing companies that don't have an aggressive licensing strategy. Such companies typically don't have extra engineering time available or won't devote it to an inventor's product. If you're approaching a company of this type, you'll need to finish developing your invention before you show it to them.