@prototype0815 Thanks for your reply! We only sell 12" x 24" on Amazon in order to help with stocking.
We are finalizing a website for custom orders (will still be US only) so I’ll edit this comment when that is up and running. In the meantime you can contact smartmirrorkits@gmail.com for custom orders.
The glass is sanded, not polished, but we can potentially do polished for an additional cost. Point taken about the 20% transmittance being preferable, but 10% produces a pretty good effect too, I have attached a couple pictures showing samples.
Disclaimer: this is still US only so sounds like myspeiegel.de is a great option for those in Europe.
Our picture:
http://i.imgur.com/K62IWDW.jpg
Album from someone else who built a smart mirror with the same type of glass we sell (MirroPane):
http://imgur.com/a/EaoG3