Currently there seems to be no offline installer for the newly released Visual Studio 2017 but creating one is as easy as downloading all features and then packaging them into a .iso file yourself using one of the many existing free burning tools such as InfraRecorder.
To download all features and languages into a local folder run the Visual Studio 2017 installer that you can download from here or, if you own a MSDN subscription, from MSDN Subscriber Downloads with a
--layout x:\FolderName switch where
x:\FolderName is the folder path where you want downloaded files to land.
For further details you can read "Create an offline installation of Visual Studio 2017".