I like how you have identified your passion and understand who you want your target audience to be. I have sold technology solutions for 6+ years to entrepreneurs and business owners- a big part of the selling process requires value-adding, which can only be achieved by understanding the minds of your target audience.
To find a niche, you need to start by asking yourself what kind of value you can bring to your specific target audience of entrepreneurs or business owners. Everyone has limited attention span these days and unless you can figure out what these people care about and how your coaching/consulting services can benefit them, it will be difficult to connect and add value for the entrepreneurs.
In short, you should determine your niche by figuring out what these folks care about and then hone your craft around providing value for those individuals.
Happy to get on a phone call if you want to talk about specifics.