I have made a guide for meeting David Bonie, but based on other guides for other achievements, I have no idea if this game is RNG, meaning things randomly spawn different for everyone, or if it is all in the same location.
EDIT:
The Pup I have met that gives me a human heart is on the Phobos Airport- and his name is Investigation Dog (Thanks to The Cherished). This is the airport you started out in, but done differently this time. Once you get your ticket, walk to the right and when you see the elevator, go down. Near the time zone there should be a dog in a fedora, who when you talk to, will say "You stole my heart".
You'll know if it was the right dog or not because the PupperDex gets updated.