A 'select all' or 'download all' images option for clients who purchase the whole gallery

Currently clients have to select individual images and add them to the download manager to download all. If they have 100's of images that's a tedious, time consuming and frustrating task when I can just send the images via a transfer or cloud facility, which isn't very professional.
Once clients purchase whole gallery there should be the option to 'select all' if nothing else, just so they can add them to the download manager quickly and easily.