The best thing you can do is keep an eye out and tag them manually. The second best is a FOIA to your county government - there's some good examples on deflock.me and templates on muckrack. But private ones are not going to be FOIA-able.

The quality of ALPR tagging does probably lag behind true counts - for example, Williamsburg, VA has 28 tagged on OSM, but 32 are listed in the transparency log (https://transparency.flocksafety.com/williamsburg-va-pd). Unfortunately not much can be done except spotting them out and about (or wardriving with a BLE beacon scanner: https://www.ryanohoro.com/post/spotting-flock-safety-s-falco...)