Is there a local place to get 3mm birch? I have had good luck with the 5.2mm from Menards, but need something a little thinner.
There’s quite a few post on this topic. I was going to post a link to one that I thought I recalled but the search turned up 24. Hope you find what you need.
My father in law spent a good amount of time recently looking for baltic birch for a telescope project. don’t remember what thickness but turned up empty handed due to russia sanctions