Mechanical Engineer / Product Development Engineer for Consumer Product

I'm looking for an experienced mechanical/product development engineer with expertise in consumer products, injection molding, and prototype-to-manufacturing development. I have a rough garage prototype that has been built and tested. The design now needs to be refined so it can survive real use, and be manufactured consistently. I'm looking for an engineer to help solve the remaining engineering challenges, refine the design, and develop a production-ready product. I need a removable attachment that can withstand household water pressure, seal reliably, attach without tools, be inexpensive to manufacture, and survive repeated use. My goal is to create a reliable, manufacturable design and prepare it for an initial pilot production run of 100–200 units. Experience with Design for Manufacturing (DFM), material selection, CAD development, and prototype refinement is highly preferred.