I believe any credible coach even one that charges substantial rates for substantial advice would be open to providing a 30 minute Q&A, in which you can try to present situations to them to see if they have the right sort of expertise and can properly communicate it with you.

Often times, you can approach other start ups with a similar product or service type and ask them who they are using. Former founders, VCs, and board members are eager to help out others within the same niches to continue to grow opportunities in the areas they already have interest in. They are also usually right on top of the knowledge waves.

Make sure you respect the coach enough to be able to take candid constructive and sometimes difficult feedback. If the coach isn't challenging the way you think and bring change to you and your organization, you probably aren't getting the value out of the relationship you need to for the rates you mention above.

Lastly, understand the difference between a coach and an area expert. Coaches are frequently there to help with broader macro strategy and the development of leadership. They can help you season faster and identify problems to proactively manage instead of being reactive to them or letting them dent your business model. Area specialists are people who can help you in specific segments or areas of the business where your company doesn't have the right mix and isn't looking to add full time talent. Think of marketing, sales management, human resources, public relations, supply chain, finance, etc.

Good luck on your hunt, I believe you will know when you have met your correct match. If it doesn't feel right or you aren't seeing clear value don't continue with it.