Jon, welcome to the boards.
I’m not a patent lawyer, but my understanding is that public disclosure of the idea is what endangers it. Before you show it privately you will want to have a NDA (Non Disclosure Agreement) drawn up by a lawyer the explicit protects the ideas you are showing privately. A product design and development consulting firm will be very accustomed to signing such a document before discussing a potential project and confidentiality is key to any good design firm’s reputation.
In Ontario there is Gibson product Design, a small firm with lots of experience in electronics: http://www.gibsonproduct.com We used to use them a lot before we brought design in house.