Ok, then the best solution is to the iframe to load those dialogs, as Patric pointed this link: Use dialogs in backoffice
Try to open this link: https://[websiteurl]/Litium/UI/frame/EntitySelectorWrapper?entityType=file (remember to change websiteurl as the domain name of your site) then you will see the dialog to select media file.
Change the entityType to page to have a dialog to select page.