This site, rockart.scot , has a Google earth map with all ancient rock art pinned to it. Including some where it says not found yet, maybe they've been written about but never located. Either way I've had a scroll about and a zoom and it's pretty good. Will be another handy resource for your walks I hope.
https://www.rockart.scot/index.cfm
https://www.rockart.scot/index.cfm
Cool site, just looking at it now during my break
https://www.rockart.scot/rock-art-database/#map-search