Have you checked Apk Mirror or Apk Pure?
I keep a copy of the apk for all my apps, using something like APK Extractor - it extracts to a specific folder, and I sync that folder to my desktop using Syncthing. I haven't installed GSam from the store in years.
You can also try Better Battery Stats.
Looks like APK Mirror has v3.4.6 here
I've uploaded a zip with a few versions in it to file.io