Not that I've ever priced one, but maybe a car cover would work? You'll only need it for a couple of months so you should get plenty of use out of it. First thing that came to mind after I stopped laughing about them poopin' on the fake owl.
We had a robin that would come to the redbud tree outside the living room window, and proceed to whack his bad self into said window for at least a half hour. Every single morning, promptly at 6AM, rain or shine, from early May straight through the end of June or so. Nesting was done, the little guys were fledged, and the little kamakazi flew off to find fatter worms. We tried hanging things in the window too. My daughters' stuffed animals seemed to REALLY tick him off. Eventually as we were all buzzing around the house getting ready for the day, we'd just wave hello as we walked by the window. Three years in a row. Not at big deal on a weekday. But at 6AM on a Saturday? Not fun. We gave up trying to keep that window clean for most of the summer, and it eventually developed a crack, but I can be sure it was because of rambo bird.
It's just me, but of it's as bad as you say, I'd opt for the cover for a couple of month of the year. Where we live, I can tell the number of small birds in the woods has gone down. No science, you don't have to be a genius to see there's just fewer of 'em. We've got enough feral cats in the woods now that they really are an issue (Feral cats aren't native to NE Pa. forests). If I started to shoot, trap, or move them I would wouldn't be helping the situation. If a bird decides to nest in the tree I was planning on cutting down this spring I wait until the fall.