Where can I get Lehmus or Leppä logs/ planks that are custom size or at least very thick)

Hello! I’m a wood carving hobbiest and I recently decided to try to carve a wooden mask. Problem is that I’m not finding good sized planks in Helsinki. I’m unsure if K-Rauta does this kind of service or if I have to contact someone else with a wood related-business.

I’m also considering walnut as an option.

I live in Helsinki and I need a big piece of wood/ plank of about 100 mm x 300 mm x 300 mm
I would like not to laminate wood since it can be more difficult to deal with glue and it might not be the niecest thing for a werable mask.

If you have any info or ideas on how to achieve this let me know!
Btw I want to be like the guy on the picture when I grow up! 😀