What to do when an implementation dependency of a java library is not available on jcenter/mavenCentral?

If java library X depends on another library Y that is not available in one of the standards repositories (jcenter/mavenCentral), then users of library X have to search on internet where “this f… library Y” is available, a library they probably never heard of and is in fact only an implementation detail of library X.
Currently, when I publish library X, I add to the generated pom enough information so that users don’t need to search the implementation dependencies themselves. I do this with publications { … pom.withXml { asNode().… } … }
Is it the correct approach? Or is it considered normal/best practice/the Gradle way to force users of a library to search where the dependencies of this library can be found?