Finding blinds for regular windows is easy, all you have to do is decide what type you want, what it will look like, measure it, and visit one of the hundreds of stores or websites that offer selling blinds. Blinds hung from roof windows or skylights require side rails, cables, or tension to hold them in place because without them they would just hang vertically without using regular blinds or curtains. You can buy different types of window blinds via

You should also consider that normal windows can be opened to the outside or moved vertically or horizontally so that blinds or curtains can be hung on the outside dimensions of the window frame, as the window does not interfere with the opening.

What type of blinds can I use?

The blinds are flat and will shut out all daylight, with some noise (eg traffic, rain) and heat. These blinds(sometimes plastic, but not recommended) are folded with an accordion and attached to wires attached to the skylight's inner frame. It is also a custom-made product but is generally less robust than blackout blinds. 

Choose aluminum or wooden slats, but definitely not plastic, as they will be damaged by the increased heat from the skylight. Good blinds are made to measure and attach to rails on the inside of a window frame or to wires, such as pleated curtains.