As koraks said, Fuji Crystal Archive is a family of papers of different kinds and finishes in Europe and it is currently the only reliable manufacturer. I add some possible sources I know of RA-4 sheets in Europe, sizes normally from 20x25 cm (8x10") or 17x24 (7x9") to 30x40 cm (12x16").
- Nordfoto: Fuji Crystal Archive DPII (my favourite) and the crappy plain Fuji Crystal Archive, avoid this one, in glossy and matte finish.
- Macodirect: Fuji Crystal Archive Supreme in glossy and matte finish.
- AG Photograhpic: Fuji Crystal Archive Supreme in glossy and luster (semi-matte) finish, sizes up to 50x60 cm (20x24"). It is in UK, so probably expect an additional 21% VAT import tax to EU.
- Retrocamera: Fuji Crystal Archive (Supreme?) in glossy and matte finishes.
- Fotoimpex: They sell a misterious "Tura" branded paper in glossy finish that seems to have a chinese origin.
- Interphoto Lab: Located in Madrid, they sell Fuji Crystal Archive (Supreme?) in glossy finish only.
- Tomcat Film: Romanian guy, I think he is also a Photrio member, cutting into sheets some limited but unsual selection of papers and sizes (Crystal Archive Maxima or Velvet matte, Fujiflex, Kodak Premier Digital luster).