There have been a lot of these "help me find a technical co-founder" posts. All the ones I've seen have missed the fundamental point: without technology, your idea is worthless. Your technical co-founder is supposed to be doing all the work, sacrificing a quantifiable high-paying job. You're networking and "being authentic". And your contribution to an uncertain venture is "[if] needed, bring cash".
The letters of intent idea is the best suggestion I saw in this post. That's about as good as you can get in terms of validating the idea before the product is even made!