Love the contact paper idea. But if your house is a rental, you might not want to try that in case it damages the window--?
Does it have to be honeycomb blinds? They can be expensive. Frankly, all custom blinds are pretty expensive (we had light-blocking honeycombs done in our bedroom recently so I know!). Since this is a rental and a unique and therefore uniquely expensive window shape, I would not invest in pricey blinds of even $600, unless you are going to be there for a long time. I like the suggestion that you use regular blinds and leave a gap at the top if that doesn't bother you.