Ask HN: How to find used car buyers

We are building a service to match local car experts with people looking to buy used car, a la FlightFox.

We're doing customer discovery/validation, but are having a tough time finding used car buyers. I think our customer segment is 25-40 year old females living in rural/urban areas. It's been relatively easy talking and finding car experts, but finding users that are in the middle of their car buying experience has proved more difficult.

Any advice on channels we could use to start conversations with this segment?