Mia's songs and arrangements are published by many different publishers. If you want to find music performed by Rajaton, you find many songs in www.sulasol.fi or here.
Many female choir songs in Finnish are published by Naiskuoroliitto. Walton Music has published the female choir favourite, Spes, originally performed by Cantus. Hal Leonard published Andromeda, originally performed by the King's Singers, and Gehrmans published the Swedish-Latin mass Diligam te and Edition Peters The Smile.
There is still a lot of music unpublished and in future you might find many of them here!