Digital BW, The Print

Your best bet for Provia or Velvia might be Badger in the US (yes, I know
you're in Spain...) - good prices and easy to deal with:

http://www.badgergraphic.com

under Large Format then film

or the view camera store
http://viewcamerastore.com/catalog/default.php?cPath=81&PHPSESSID=3d7927da3f
ca4dccf2b7ee79dcd2b6ad

But it's 20 shts for $100...

(I think only Fuji makes 5x7 transparency now? and even silverprint in the
UK doesn't list it. I think Badger imports it directly from Japan) You could
also try asking the people at Lotus Cameras http://www.lotusviewcamera.at/
or Linhof Studio in the UK http://www.linhofstudio.com/index.html