You’ll occasionally see some posted on marketplace or c-list, but if I were you I’d put in some time door knocking in areas you are interested in.
I’d also have a letter typed up with your intentions and leave that on the doors of people who aren’t home.
Use your county’s GIS site to find the owners. If they live far away, send them a letter (the site will have their address but probably not their phone number).
There are paid people search sites that will get you their phone number, but I’ve never tried one before.