Just get an all european map :)

E.g. this one: osm.wiki/All_in_one_Garmin_Map

Sorry, but this file is to big (just have a light DSL-Connection and 2GB Micro-SD-Card)...
Any other ideas?

Go to this webpage and pick the tiles you want: http://garmin.na1400.info/routable.php
The map tiles will be a bit bigger than just Crete, but it shouldn't take too long to download.

Or - go to Cloudmade downloads for Greece - oddly Turkey is not listed - guess they split crete in two - see here - http://downloads.cloudmade.com/europe#downloads_breadcrumbs

Could be a small enough area for you to load into JOSM and make your own custom one via MKGMAP