Blackout roller blinds with box and side rails for darkness

Hello
Since the bright days/short nights are starting again soon, we are looking for blackout blinds for our windows (140 cm wide and 125 cm high), but we are looking for a high-end solution, because the standard blinds that you usually find and mount on the wall still let in so much light on the left/right/top/bottom that the room is relatively bright. We are looking for ones that completely darken the room, where the blind is basically housed in a box that is mounted on the wall and the blind sits in side rails that are mounted on the wall, preferably also disappearing into a guide at the bottom and it is pitch dark. Basically, an internal blind in the style of an external roller shutter. Our junior and I wake up at the first ray of sunshine that shines into the room, which is pretty uncool when it’s still “in the middle of the night,” okay if I’m awake I get up and do morning exercise, but my 2-year-old son is rather a cranky burden then ;) Also, he has trouble falling asleep in the evening if the room is not dark.
I haven’t been able to find anything so far, does anyone have an idea/tip where you can get something like this without having to create something DIY?
Subsequent external roller shutters are ruled out for aesthetic reasons on the facing facade.

Such blinds (with rails on the sides) are available for direct attachment to the window. I just don't know if they also completely darken at the bottom. We are still getting our blinds for the roof windows - but they can be obtained in all sizes.

Found some at Raumtextilienshop de... they have some that are built like a roller shutter (but with normal blackout roller fabric) including side and bottom finishing rails, but a roller (with white backside, 1.45 x 1.40 m) costs 250 euros... If you want to outfit a room with it and absolutely don’t want an external roller shutter on the outside, it’s certainly still acceptable, for us it would be 4 rooms, so that’s 1000 euros gone.

Therefore, I will try a normal roller and build a box from laminate board for it and install appropriate side guide rails/finishing rails and attach a breast molding to these for better sealing. Maybe it will work =) It’s still too cold for gardening anyway