Cheap fix to your problem.
I went out and bought one of these (pic at end)
I shaved off the most bottom part, took out the rubber, and just tightened it as much as I could, impossible for the window to go any more open than what I put it at
I put it in because my dog loves to put her head out the back window, an she kept opening it with her body and trying to jump in the bed.
Problem fixed
ps, if you cannot find one of these, I'll happily send it to you. Free(just pay me the 2$ shipping for it)