Well done!
I'm Finnish and I couldn't think of any other common -aija names. All the 6 you have are real names, some of them really popular.
I searched the database of all the first names ever registered in Finland and I found Laija (6 girls), Haija (5), Paija (3), Vaija (2), Daija (1), but I hadn't heard them before, and can't tell for sure if they're made-up or foreign (the site doesn't of course tell the origin of the parents).
Maija is one of my favourite names :)