Chios has/had a free walking map (or actually a set of maps with accompanying booklet) available from the local tourist office, also available online courtesy of chiosnet.gr. I doubt if it has been updated lately, and it was of limited use even when I visited years ago. It is, at least theoretically, available in several languages, but I could only get hold of a German copy myself. Lucky I had German at school also then… But there you have it:
Local Maps III
Dr. Georg Perreieter’s old map of Amorgos is a classic, but probably not on sale anymore, it shouldn’t without a serious update. Outdated even when I used it, ten years ago.
Local Maps II
Folegandros is another lovely island with a good local map of footpaths:

ΦΟΛΕ- ΓΑΝΔΡΟΣ FOLE- GANDROS
Local Maps
Some good local maps also exist. E.g if you are visiting Tilos you just *must* buy their famous “Blue Map”, the Nisos Tilos, which is the original footpaths & road map for this very nice little Dodecanese island.

Nisos Tilos
It is also available online, but that one is not completely updated.
Maps
The good map series you can find for the Greek islands also in most cases will show the major footpaths. Some even include walking guides. Always ask for these from local bookshops and shy away from cheap tourist maps that are drawn it seems often from pure fantasy wrt both paths and roads.

Road Editions

Anavasi Topo Islands
Walking in Mani
There are walking guides for mainland Greece too, of course. When I visited Kardamili I bought the above book, “Walking in Mani (Book 1)” by Mat Dean. Not sure what has happened to this intended series (obviously?). There is a new book now, “Inside the Mani – a walking guide” by the same author, covering the same ground:
There is an accompanying web page at http://www.insidemani.gr/, but their book shop is dead, so I am unsure if even this one is still in print. Check local book shops. If not available anymore there are several other alternatives, including Sunflower Books and Marengo Publications.
A Walking Guide to Aegina
“A Walking Guide to Aegina” by Gerald Ephraim Nektários Thompson is more than ten years old now and in need of an update, but still a good booklet with some hand drawn maps of more dubious quality. Lots of information (perhaps too much for a walking guide) about history etc built into the text makes it a bit hard to follow at points. But still I am certain you will have lots of fun with this one too! Available in bookshops on the island.
On Foot in North Lesvos
This is an excellent booklet with at least some overview map. It is sold locally and at Amazon. In my experience, the best walking guide for the north of Lesvos, with very detailed walk descriptions, and it’s even updated every year it seems. Keep up the good work, Mike!
The Bleasdale Walking Map of Paxos
Paxos has been mentioned before, and not without reason. Paxos just about the ultimate little Greek island. What I have not mentioned yet is “The Bleasdale Walking Map of Paxos” by Ian & Elizabeth Bleasdale. This book can be bought locally. Actually I am not sure if it’s a map with an accompanying booklet or a booklet with a map. Regardless it is excellent and the most detailed description of the Paxos path system that you can find.
Alonnisos On Foot
Nearby Alonnisos has this book sold locally in English and Danish. For more information and updates see my Alonnisos page.