Juanne e Matte (excuse the spelling) opposite the Repsol garage in Altet used to have a lot of surplus no longer stocked tiles in their yard; basically leftovers from bigger orders. They were in bunches around the perimeter fence and if you asked in the office they were OK for you to go hunting. They told me that if a tile was over 5 years old you would have difficulty finding it anywhere.
Looking on Google earth it seems to be called Juanjo now.
Worth a try.