How might I find manufacturers for someone starting a small business?

A good friend is looking to start up a new business. He is a long time student, and has some clever ideas for backpacks/bookbags. He has spent the last year planning and saving up starter cash and is in the process of having prototypes made… but he needs a manufacturer that will make special order pieces, and has asked for my help.
Where should we be looking? What should we be looking for? Is there anything we should avoid?