There’s a conservation management and cultural tourism plan for Glenrock Lagoon online at http://www.environment.nsw.gov.au/ that is a wealth of information about all the ~150 historical artifacts in the area!
…including GPS location details!
After a bit of poking at python, I got the UTM information uploaded to a GPS, and a GPX file of all the waypoints is available from here. (For best results, open this file in Google Earth!). You will need to read the report to make sense of what the waypoints are… But no more stumbling across things at random, like I’ve been doing for 20 years! :)