Shameless plug, I'm selling such wooden "sheds" (in Italy, but could ship EU-wide if required) with up to 45mm thick walls (mostly garden / leisure / party oriented though) on my website. I'm willing to give a little discount if any fellow HNers are interested (sorry, you'll have to use Google Translate - it's in Italian :)

https://www.h2oreca.it/cerca.php?categoria=giardino%2Fcasett...