I have a similar need to contact local businesses, so I am also interested in anyone else's experiences about this.
I already frequent small local services and restaurants, so I occasionally go out of my way to attend owner-operated store fronts at odd hours when they might have more time to talk. I'm pretty sure being a paying customer before/during our conversation greases the wheels a bit, but that tactic would be very expensive to scale out. Also, not all services of interest are owner-operated, and even if they are the owner often leaves during the slower shifts.
The other approach I'm contemplating is surveying the customers of local businesses as they come out to the sidewalk, and then sharing any useful business-specific survey results with that business for free. I need to complete these surveys as part of my own customer development work, so sharing business-specific findings seems like any easy win-win (assuming I can get sufficient participants and keep them anonymous of course). Has anyone else already tried something like this?