I have worked in technology sales for 6+ years now and have seen firsthand how SMB, high growth mid-market, and Enterprise companies structure their sales teams.
To your point, small and medium businesses have sales reps directly reporting to the CEO because there is NO need to have a middle layer of sales management. I have seen so many smb companies run without a head of sales because they have not reached the level of scale that requires a revenue leader. You're saying the above is a bad fit; however, many smbs who don't plan to scale are perfectly happy with the status quo because it works for them.
If your opinion is different than theirs, it will be on you to demonstrate the business-tangible value of having someone run their revenue operations so they can focus on strategy, vision, etc. This requires building tailored business cases to each CEO that you speak with.
For the SMBs out there, it will be incredibly difficult to convince CEOs (all CEOs are essentially evaluated primarily on revenue generation) to hand over arguably the most important part of their business to someone else.
That being said, I would start by examining which clients you have historically had success working with and use that information to create multiple lead generation campaigns to go after similar companies. Happy to get on a call and walk through a lead generation process for your service (inbound leads, thought leadership, email marketing strategies for outbounding, etc.)