I think you're referring to a roman shade which is definitely used without curtains in a lot of instances. Your best bet is to go to a retailer with a picture of your window to discuss options. I think it's difficult to order online for a unique case and be satisfied. Unless you're living in a rural area there should be somewhere you can go to look at options. Custom window treatments are amazingly expensive and when you get motorized that adds another layer of cost. However, if you buy something with a good warranty they last a long time.

I also recommend having a film installed on the windows. The problem I have with roman shades is that they're either up or down, there is no middle ground. If you get blackout shades you definitely won't want them down during the day. Any amount of sunlight will eventually fade fabrics and discolor carpet and wood floors, even in a north facing room.