Start with the startupy books and it might be easier to get ahold of the publishers. Plus you might get a bit of an influencer impact when they share on social.
Think about how masterclass does it, then niche down into startups and follow the playbook.
Feel free to ping me (email in profile) if you end up going down this path and need suggestions for initial folks to reach out to.
Oh actually, while you’re on the front page of HN, drop a contact form on the page with something like “interested in having your book hosted?”
Might “fill the funnel” with even less work. Good luck!