Three shops I often buy paint from, Bob Ross or not, in Holland are 'De Kwast, Van Beek art & Martin Brinkhuis. The latter is my favourite.
Bob Ross paints aren't cheap and I prefer 'Winton' (from 'Winsor & Newton' but then budget quality) and 'Van Gogh'.
Veel succes met uw zoektocht!
PS: You might even try Amazon.nl but I have no experience with them.