Hi All,
I am living in the very south of Spain and have had similar problems finding pastured organic animals. So in desperation, I have started myself to produce for family and friends.  My in laws have an organic farm, beef and chicken in small numbers, but as the whole organic industry is crashing in southern Spain, nobody can finish or kill organically certified cattle in our area.  I convinced them to switch to grass finishing last year, and slowly we are turning out organic pastured beef.  We killed a cow last week, and will hang it for 4 weeks minimum before sharing it out to family and friends.  I believe that in the north of Spain there should be more production, but I am not aware or any.  Asking around in health stores will eventually lead you to someone. 
thanks
Francis