The typical smart mirror film is Gila mirror window film (https://www.amazon.com/Gila-Privacy-Adhesive-Residential-Control/dp/B000H5XTKG). I got mine from Lowes in the U.S. It is a lot cheaper than two-way glass, and the quality isn’t mind-boggling but it’s not bad either. I think it’s 30% transparent but you can check that through the link. I applied my film to acrylic and it worked well enough–I’d recommend it if you’re on a budget.

Also based in Denmark like @mdhenriksen and considering going the foil route for a frameless 32" bathroom mirror. What about interglas.dk? Have you tried them? I’m contacting them tomorrow to see what the price is - as the in-site calculator they have says for 70x40cm the mirror is 50€ + shipping :astonished_face: