Do window shades with vertical railing exist?

Question

I've been imagining a type of window shades that would roll up and down inside vertical rails attached to the sides of a window frame, so as to completely block the light.

As seen in Velux windows: http://www.domwebx.com/Preben/LightBlock_Shade.html

Up until now, the only blackout shades I could find are not guided by such rails. This doesn't block the light from entering on the sides. Do such a thing exist in the USA, and where can I get one?

Alternatively, I could probably fit some railing system on the sides of a window frame. In this case, what system would you advise me to get?

Answer 1

Hmmm, how about the one for which you provided the link!