I have only every worked with a few hardware consultants.
Some have worked for free.
Some have charged a few hundred dollars.
I have never understood who they work for or where their interests lie.
More recently, it occurred to me that I have never signed a contract with one and that I very likely am assuming all liability for their work.
So, I just did a search for “independent hardware consultant” and got several promising hits.
If I cannot write such specs myself, are these consultants the way to go?