Reddit reviews Mirror Vertical Blinds PVC (Made-to-measure sizes)

The trick is to have closed blinds on the other side of the insulator. This should give a fairly normal appearance if they fit and look right.

If all else fails, you can always implement a thick, dark, high quality fabric that resembles curtains. If that's not enough, you can make a wood or wire frame to give the fabric inward depth from the miniblinds and glass. If that's not enough, you can further add a lamp between the insulator and fabric to simulate a lit room, and you can even incorporate a window A/C since they are visibly insulated a lot of the time anyway.

It's all about determination, my friend :)

Edit: Mirror blinds are a great style for this purpose. They're aesthetically appealing and I'd be really surprised if someone thought it was unusual that they couldn't see past reflections in broad daylight. Try to use an insulator that blends in well with the scene and, if you still feel it necessary, open up often enough to mitigate any long-term neighborhood concern.