University and health system spinouts
Your other buyer, and a genuinely different market. The company often does not exist yet, so it cannot be found in any register of companies. It is found through the office that licenses the science and the faculty founder behind it, both of which are nameable a year before there is anything to sell to.
Who signs: director of technology transfer, licensing manager, incubator or accelerator director, the faculty founder, and the first hire who is a real operator.
Roughly 190 to 220 institutions
US research universities running a technology transfer office; the spinouts themselves are not enumerated anywhere public until they incorporate