Google Play Services aar download for above 11.0.4
Following are the details from Android developer documentation:
Programmatic access:
For programmatic access to Google's Maven artifacts, you can get an XML list of artifact groups from maven.google.com/master-index.xml (link) which gives the group path
Then, for any group, you can view its library names and versions at:
maven.google.com/group_path/group-index.xml
For example, libraries in the android.arch.lifecycle
group are listed at maven.google.com/android/arch/lifecycle/group-index.xml (link).
You can also download the POM and JAR files at: maven.google.com/group_path/library/version/library-version.ext
For example:
maven.google.com/android/arch/lifecycle/compiler/1.0.0/compiler-1.0.0.pom. (link)
For more details please refer: https://developer.android.com/studio/build/dependencies.html#gmaven-access
For complete list of Google Play Services libraries, refer below xml: https://dl.google.com/dl/android/maven2/com/google/android/gms/group-index.xml
Eg: To download Google Play Services Location library AAR file, use the following link:
https://dl.google.com/dl/android/maven2/com/google/android/gms/play-services-location/11.6.0/play-services-location-11.6.0.aar
You can replace group name, version, file, extension to download other files.
Note: Do check the pom file for each module, it may have dependencies on other Google Play Services libraries. If so, you will need to download all dependent files.
[Update]:
You can use Google's Unity Jar Resolver for this:
https://github.com/googlesamples/unity-jar-resolver