Look here for specific version numbers: https://support.apple.com/en-us/109033#latest
Then follow these steps for Sonoma (14.8.7):
softwareupdate --fetch-full-installer --full-installer-version 14.8.7 hdiutil create -o /tmp/Sonoma -size 16000m -volname Sonoma -layout SPUD -fs HFS+J hdiutil attach /tmp/Sonoma.dmg -mountpoint /Volumes/Sonoma sudo /Applications/Install macOS Sonoma.app/Contents/Resources/createinstallmedia --volume /Volumes/Sonoma --nointeraction hdiutil detach /Volumes/Install macOS Sonoma hdiutil convert /tmp/Sonoma.dmg -format UDTO -o ~/Desktop/Sonoma.cdr mv ~/Desktop/Sonoma.cdr ~/Desktop/Sonoma.iso rm /tmp/Sonoma.dmg
Or for Monterey (12.7.6):
softwareupdate --fetch-full-installer --full-installer-version 12.7.6 hdiutil create -o /tmp/Monterey -size 16000m -volname Monterey -layout SPUD -fs HFS+J hdiutil attach /tmp/Monterey.dmg -mountpoint /Volumes/Monterey sudo /Applications/Install macOS Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/Monterey --nointeraction hdiutil detach /Volumes/Install macOS Monterey hdiutil convert /tmp/Monterey.dmg -format UDTO -o ~/Desktop/Monterey.cdr mv ~/Desktop/Monterey.cdr ~/Desktop/Monterey.iso rm /tmp/Monterey.dmg