Below is a list of Companies that sell ferns suitable for Terrariums and Vivariums
Dartfrog
Bens Jungle
Araflora
Carnivors and More
Terra Erfordia
Monde des fougeres
Dartfrog is the only company based in the UK, the others are all in Germany, Holland or France
Some sell a number of Selaginella species (once classified together with ferns) as well
Information supplied by Richard Hayward