Licensed Professional Contact List Builder

I run a licensing marketplace and need to build contact lists of licensed professionals across various trades (e.g., HVAC, Plumbing, Electrical, GC). Much of the contact information needed will be for individuals or small 1-2 person businesses, which makes this fragmented and not always easy to find through standard tools. I need someone who can bring a real strategy that has worked in the past — whether it be marketing, manual sourcing this contact info, proprietary lists, etc. The goal is to get these individuals to my website and potentially for reaching out to them (cold email or other direct outreach) if you have experience with that as well. If you have had success with a similar project, tell me briefly how you'd approach it. Will likely start with a paid test before discussing larger scale work.