Artifactory Proxy Issue

We have a private Artifactory in which we proxy all our dependency retrieval through.
We are encountering issues using this to get gradle plugins and i believe it is due to the using the wrong url/access.
The issue is the sonarqube-gradle-plugin which can be found on the plugin search but i cant seems to find it via the normal repo layout
Which does a redirect to
Which makes me assume that the plugins are hosted on bintray but in some private redirected repository?
Is there a method of adding the plugin repository as a remote repository and if so, which url?

Thanks in advance,