How can I change the default media library path in Sitecore 9?

My company uses a multi-site configuration where each Site node has it's own media folder. After upgrading from Sitecore 7 to 9, I no longer have the access to upload / access images from the media browser to a path outside of the default Sitecore Media Library. How can I change this?

For example:

Sitecore>

     Content>

          MySite1>

               Media> (I would like to access this folder)

          MySite2>

              Media> (I would also like to access this folder)

Media Library> (I can only upload or access this folder and sub folders with the built in media browser)

 

Thanks!