Wow thats nice, but I don't imagine a real Finish sauna without wood inside in it. If you are afraid that it requires a lot of preservation, then you shouldn't worry because you could use burnt wood that is very durable. I used it in my sauna 5 years ago and it still looks nice. This company -
Degmeda.eu can get you everything you need, so feel free to contact them:) I hope it helps