How to find homeowner to offer buying their house

[David Santore]

There's this 2 family house I've eyed for the last year, been on the market twice but hasn't sold. It's not on the market now, but I want to buy it. The owner doesn't live there from what I'm aware of. I spoke with my real estate agent who spoke with the owner's agent. The owner's agent passed our message along but hasn't heard anything back from the owner, even after multiple times reaching out. The easy answer is, "Welp time to move on" but I want to turn over every stone. Maybe the owner is switching agents and doesn't want to talk to the current one? Maybe they're just putting it off? I'd like to reach out to the owner directly and make an offer (I'd still work with my agent since this is my first house). I know this is becoming more common in today's market (Boston), but I'm not sure how to approach. Do I just search public records and send snail mail? If anything I'd do certified so I know it's being signed to receive.