Help develop a technical design spec for an electromechanical product

I am looking for assistance with developing a technical design spec for an electro mechanical product that will be used for consumer purposes. this spec, needs to be developed so that a designer or design company can take the detailed specification and develop the product from it. Regarding overall design, I have quite precise specifications in mind for the product, and may be open to flexibility depending on the situation. The basic design concept is an arduino processor at its core controlling a stepper motor. the software and hardware requirements have already been developed, basically we're talking about taking these already developed requirements and putting them in a document specification that is formatted appropriately and specific enough for a designer to have enough information to use it to design the product. If you have experience in developing specifications for electro mechanical products, as well as design and architecture for this type of electromechanical device, please contact me to discuss further. Thank you for your time and consideration.