I do not have information for tour companies in Greece but here in Turkey, we have cruise lines and packages that include island tours. Some longer ones do include Athens and some other cities along with the islands tours.
Cruises can be a different experience.
You can take a look to
+ http://www.etstur.com/Etstur-Gemisi-Vizesiz-Yunan-Adalari-Turlari (unfortunately in Turkish but you can use Google Translate).
+ http://www.prontotour.com/Yurtdisi-Turlar (this is the one of main and biggest tour companies in Turkey -- you still need to use Google Translate).
Let me know if you need any help.
sas over 6 years ago