Spread the word to contacts in your network and have them talk to people in their technical circles. Maybe you’ll get lucky and find someone with time and interest.
Hire an undergrad ME student with appropriate design experience from a local university over the summer for a couple grand.
Maybe you can find a wiz Ph.D. design student who could use some extra cash on the side.
Another approach might be to teach yourself what you need to know about materials, machine design, or whatever and put together a really solid product to pitch to venture capitol, a company, or consultant. Might want to talk to any business contacts you have about options for the invention process, or read some books on the topic.