I think you are near Chania, Rej? If so I would recommend Theophanis Lambrinakis. He is a private ENT specialist who can certainly do the hearing test for you and provide the hearing profile needed in order to get a hearing aid. I am not sure if he can actually supply the hearing aid itself but I am sure he will be able to tell you where to take the prescription. Both my late wife and I used him for other ear problems and found him very professional and not expensive.
Contact details: Land Line 28210 28003 Mobile 6945 947943. He is at 17 Tzanakaki Street, Map here
. As you walk up from the National Bank of Greece the building is on the left hand side just before a large café. There is a passageway and the entrance is on the left hand side about half way along the passage. Not sure which floor he is on but there are signs in the window next to the door.